Travel as Oregon Trail

I’ve been trying to think of a way to run a journey overland in my game (motivated by picking up Adventures in Middle Earth). I don’t think it’s super interesting to play a normal D&D game out over weeks of travel time (after all: “We keep going in the direction we’ve previously decided to go” seems to cover pretty much everything). We’re introducing a system precisely because we want to have a machine to spit out the results of travel; if we were willing to use the normal adventuring rules, we’d just use those. If the most interesting thing that the system can give us is “you aren’t lost today, and you make your camp in a site which is ambushed that night by 3 black bears. Roll for initiative, you party of twelve level 10 characters”, I don’t think we’ve accomplished much.

These rules assume my long rest houserules; you can’t long rest while roughing it and can only long rest one night in seven anyway. So depletion is a real risk, and it lasts with you until you make it to the end of your journey.

The procedure: Travel is broken down into weeks and days, which are themselves the basic unit of resolution until something goes wrong, at which point the game zooms into an appropriate resolution for what went wrong. Use the usual rules to determine pace, hours marched per day, terrain difficulty and so on.

Each day:

Each day, the expedition leader makes a Wisdom (survival) check against a DC based on terrain:

  • DC 5 (grassland, meadow, farmland)
  • DC 10 (artic, desert, hills, open sea with clear skies)
  • DC 15 (forest, jungle, swamp, mountains, open sea with overcast skies).

On a success, the group continues on that day, taking appropriate precautions and making good time. On a failure, resolve a┬áTravel Mishaps (see below). And side note: instead of making that check, consider using the Mob Attacks chart (DMG page 250) in order to quickly collapse a number of days down to just the exciting ones. This does mean that a trained ranger can take journeys of fixed lengths without mishap — is that so wrong?

Regardless, each character not proficient in Survival consumes one ration.

Travel Mishaps

First, figure out the weather (DMG page 109). This won’t affect the difficulty of daily travel (that roll includes compensating for the weather), but will affect resolution of the remainder of the travel mishap.
Since weather is based around interesting values being 3/20ths of the total space, we can make a 3d6 roll:

  • 1 colder, 2-5 normal, 6 hotter;
  • 1-4 no wind, 5 light, 6 strong;
  • 1-4 no rain, 5 light rain/snow, 6 heavy rain/snow).

Random things that could go wrong:

Delayed: The party loses 1d10 hours of travel time.
Lost: The party is lost, having spent the last 1d10 hours going in the wrong direction, and has disadvantage on Wisdom (survival) checks until one is succeeded (at which point they have regained their bearings).
Hazard: There is an unforseen obstacle (rockfall, flooded brook, lost bridge, etc); it must be overcome either by engaging a solution around it or traveling 1d10 hours around it. Overcoming likely requires a DC 10 Strength (athletics) or Dexterity (acrobatics) check from each character, with a penalty of 7 (2d6) damage from a fall on a failure.
Someone is poisoned: Any character eating foraged rations is exposed. Those failing a DC 10 constitution save take 6 (1d12) poison damage and are poisoned for 24 hours.
Someone is diseased: Any character drinking foraged water is exposed. Those failing a DC 10 constitution save acquire Sewer Plague (DMG p 257)
Supplies are destroyed: Each character loses 10 lbs of rations to animals and spoilage.
Rust, rot, and ruin: Each character must make a DC 10 Intelligence saving throw; those failing: Each armor, weapon, or shield is at -1 to attack, damage, and AC (per rust monster). Each scroll or potion has a 50% chance to be destroyed. Each spell in a spellbook has a 50% chance to be destroyed.
A monster is spotted
A monster ambushes you
Tracks are discovered
The weather shifts unexpectedly
The party is delayed

d% Result Effect
01-25 Delay 1d10 hours of travel wasted on delays, detours, etc
26-30 Confusion Disadvantage on future Wisdom(survival) checks until one is succeeded to navigate; party travels 1d10 hours off course each day until then.
31-40 Injury Pick Strength(athletics) or Dexterity(acrobatics). Each character failing a check against the terrain DC takes 7 (2d6) damage from the travel, but cannot be reduced below 1 hit point as a result of this damage. If it has rained in the last week, the check DC is +5 and the damage is x2.
41-50 Disease Any character drinking foraged water must succeed at a DC 11 constitution saving throw or acquire Filth Fever (DMG p 257). If it has rained in the last week, the disease is Sight Rot instead (DC 15).
51-60 Rot Each character must succeed at a DC 10 intelligence saving throw or else lose 50% of their rations, potions, and scrolls. If it has rained in the last week, the DC is +5 and the damage is 75%.
61-70 Ruin Each character must succeed at a DC 10 intelligence saving throw or else their arms and armor are at -1 (per rust monster). If it has rained in the last week, the DC is +5 and the damage is -2.
71-80 Abnormal Weather Heat wave or cold snap for 1d10 hours. In arctic or desert environments, treat as delay.
81-90 Inclement Weather Precipitation (or heat wave, in desert)
91-99 Storm Snowstorm, thunderstorm, duststorm
00 Powerful storm Blizzard, hurricane, tornado, downpour (desert)

The Nether

The Nether is my shadowy/misty/ethereal plane. It was pretty much fated to work out that way, if I think about it.

The 4e plane of shadow is a place. It’s a gloomy place, with a lot of undead. It’s got dirt and trees, though. Oh, and it’s associated with death and dying, but it’s not like any rules really underscore that; for instance, ghosts don’t shift there during a haunting (unless I missed an awesome adventure or something).

The 3e/5e ethereal plane is a transitive plane. It’s “backstage” of the world: you can see the world hazily, but you can’t (generally) interact with it. Ghosts and phase spiders, maybe other monsters, are tied to it. But most undead aren’t; they kept their shadow plane-y associations, and so ghosts are somewhat unusual in that they explicitly go ethereal. And in fact, nothing goes shadowy; in Volo’s Guide, we got the planar-associated Shadow Mastiff, and its rules interact with the Ethereal plane (NOT the Shadow plane).

So, wham, they’re combined. The Nether Plane is like space, empty. Also like space, you can move physically away from the world (“up”), moving away from everything until surrounded by the void. And sometimes, if you are very lucky, find somewhere new, leaving the Deep Nether and finding a new place.

It has currents, so it is sometimes described as a river (or even multiple rivers). This is where the Styx is, and the other four rivers as well. Sometimes the current is so strong that the Nether seems almost solid, but it doesn’t have material; the current doesn’t seem to be manipulable in any useful ways by anything less than magical coercion.

Charon, the boatman of myth, definitely has equivalents here: pressgangs of devils, headhunter valkyries, scavenger demons. The currents play a huge role here, since the dead tend to be confused and unconscious, so get swept into these machinations quite easily.

They also lead to a nautical theme. If I want my spelljammers, my extraplanar ships, they’ll be Nethercraft, sailing the land of the dead from world to world. Gates and worldfalls are probably manipulated via enormous human sacrifices, altering the flow of the Nether and bringing places into (or out of) conjunction.


The Endless City

I’m stealing this from Patrick Stuart, as with all of “my” good ideas.

This is a plane. It has settlements embedded inside of it. Its organizational principle is simple to describe, but (and this needs to be stressed) it’s infinite, so any finite account of it is necessarily incomplete and contradictory. I’d been calling it the Astral Temple, but as I thought about my needs, the word Temple as a generic organizing principle for this place has become less useful. And Astral, as an adjective, I don’t find useful to describe what I’ve wound up with there. Previous editions of D&D named their planes and then added detail, which is how we wound up with the Clockwork Nirvana of Mechanus — it had been called Nirvana, and then we decided we wanted gears. Here, I’m willing to ditch a name that’s not serving me any more.

Imagine Relativity, that famous Escher print. The City has the same color scheme; chalk-white marble, black granite, grey lead, black iron, white ash. “Down” depends on where you stand; while each point in space has such a down and it is independent of terrain, it’s obviously not uniform, and there are areas of hyper- and null- gravity, twisty corridors which war between bases, ceilings that become walls that become floors. Light is eerily without source: similar to a blacklight, white objects emit their own glow, and a large proportion of the stone is white. The white lights throb gently, breathing minute-long exhalations of glow. Explorers use white sheets to see by. Where the sky can be seen, it is a grey static cloud mass, gently a-glow, in every direction.
The stone and iron and lead are growing, too. An archway that leads down a staircase studded with alcoves will find those alcoves becoming archways to new galleries spotting framed mirrors and new fountains. The pace is sedate but continuous, with the floor of a room seeming to drop a few inches every year. The seeds of architecture yet to come can be dug out by miners, twisted doorways and bonsai statuary foetal in the rock. 

Everything appears hand-made and decorated, full of meaning. Every lintel is inscribed with a poem, every flagstone a mortuary marker, the cobblestones mixed with potshards bearing scratched receipts for grain sales. Windows of a thousand styles offer views between rooms equally ornate: perhaps an arabesque grate on one side of the corridor permits a view into a gothic stained glass arch on the other side, for all the world like the alleyway between a church and a mosque. Perhaps a chimney offers views through grates, grilles, pits and firedogs into smoking dens, caves, wainscotting, screens and plaster. Books and scrolls and tablets and carvings and paintings can rub shoulders, for all the world like an antique shop.

Everything is eerily quiet, the vast stillness of the place drinking sound. There are still-working fountains sometimes (the strange gravity of the place sometimes settles into a sort of perpetual motion), and their bubbling trickle feeds mosses and vines. A patient traveler can hear the vines expand, growing towards white marble on grey-brown tendrils.

The Gates of the City

The City is a leaking sieve of manufactured spaces, due to its odd relationship with gravity and topology. A city square might have a plot of grass with a tell-tale force shimmer. One who stepped upon that grass might find themselves vertiginously between planes for a moment, in the City but also on the Talenta Highlands of Eberron, smelling the saurial dung not five feet away. The City generally has a negative pressure, pulling material from the plane to which they are attached into itself. However, this current can sometimes be opposed (as though it were a cataract of rushing force), and varies in strength, sometimes pushing outwards.

Often, gates respond well to certain objects or behaviors; there are tales of gates which respond to the touch of an elf, the sound of a drinking song, the presence of a laurel wreath. Myths persist of doors which open to the touch of a faithful man, in the time of truest need, or when a millenarian cult’s faithful fulfill their prophecies. However, in most cases, it’s simply time and conditions: sunlight, storms, the angle of the stars.

Wherever a gate appears in the temple (whether a coterminous plot of land or a freestanding active gate), the area around it takes on some nature of the other sides’ character. Of course some of this is due to infiltration from the gate: dandelion seeds or horseflies might cross over during an inhalation, or a lunatic poet. But more frequently it is a natural process of the city itself: the architecture matches the style on the other side, the statues the people, the writings the language, through no obvious process.

While any border or archway can form an attachment to the city, manufactured doorways, mirrors and paintings seem particularly to do so.

The Contrafactuals of the City

There’s another insidious pattern to the art of the city: it never happened. The statues are of kings celebrating victories they never tasted, queens where there had been kings, tyrants who had been kind, princeling descendents of lines ended in bloody revolution. Not everything is always a lie, or at least not obviously so (a painting portraying a general on a white horse they did not ride seems more like acceptable artistic license than a lie), but it remains the fact that the City gets things wrong and extrapolates.

A stairway with the busts of the rulers of Bretonia (each set in an alcove) likely gets several of them wrong: this one with a scar they did not have, this other one listed dead as a child, and each one after that a foreign monarch from the Black Forest instead. And perhaps a doorway off of the staircase, leading into a library whose books are in that barbaric sylvan tongue, outlining how victory was achieved in the conquest the reader knows did not end that way. And perhaps a doorway to a staircase from there, leading into a corridor whose windows describe the life of a baker at the edges of the Black Woods, littered with sacks of worthless ash. And from there, doorways at either side: one of portraits of a minor noble miller’s family, and the other to a statue of a sailor holding a rat pocked with plague.

Another example of this is where two rooms abut each other, a newly developed third one might show a confused view of history, spawning imagined interactions and consequences which never could have happened. This sprawl spreads in both directions, flourishing in infinite variations as it climbs.

Artifacts removed from the City age poorly. The iron rusts too fast, the stone is soft and crumbles, paper goods rot within days. Caveat emptor.

“Up” seems to lead mostly towards imagined pasts and consequences, melded together from the old growth of imagined events. The further “up” one climbs, the murkier it can sometimes become; the risk of an intersection with some other branch of the City greatly increases, and the odds of the results becoming a muddled mess increase dramatically.

“Down” seems to lead towards gates to places and times which have that nature of the real which the black-and-white City lacks. It doesn’t point “into” the gates, so much as into clearings which contin the gates: gates tend to orient in a clearing, and paths tend to lead downwards towards them. Not all gates define such a down, and which gates do seems to be quite random, but the fact remains that heading down will often eventually find gates and, possibly, civilization.

The Contrafactual Gates

The final wrinkle in the City is that not only does it open onto a thousand thousand worlds, not only does it contain the works of a thousand thousand possibilities: it opens onto possible worlds. That is to say, at the end of a historian’s search through the rooms of the City into a place they believe to be a seeded gateway from which the other rooms of the City were derived, they determine the passcode for the doorway and pass through. The space they pass into might be a whole and vibrant world, connected through other portals. But it might also be a smaller shadowy slice of a world, distant in time and space, closed in on itself. A traveler might have found a path through the City which connects to their own world twice in two different locations, but perhaps instead the second connects to a shadow of their world, reflecting historical changes like those in the City.

These Shadow Worlds can be a dangerous trap, since they may not be stable. Sages conjecture perhaps that is the way of the City at all times, absorbing whatsoever it connects to. This has (eventually) dire consequences for all of the worlds which touch The City.

Monsters in the Wilds

Where the city grows strange, far into the maze of rooms, there are often impossible creatures lurking. Sometimes they’re creatures called in through a gate or set by some ancient mage to guard a gate. Sometimes they’re hypothetical creatures, who might have been called up by some ancient mage to guard a gate, had that mage existed. Sometimes they’re forced out from a settlement formed around a gate, grown strange and large in the distance. And sometimes, they come from Outside.

The Citizens

Many factions cluster in the city around its entrances and exits. These places represent safety and security for those who hold them: an extra way to leave, access to fresh water, air, and food, and trade opportunities. Some factions hold sway across large swaths of the City, expanding their borders and establishing their law. Others exist within others’ settlements as a philosophical bent or a simple social club.

Modrons. The mechanical modrons are a race of self-replicating constructs which seems to originate in the City. They are made of its grey wood, soft stone, and hard iron frames. Their disturbingly fleshily-rendered eyes and lips are set in geometric bodies. They single-mindedly destroy all art with which they come in contact, which can frequently set them at odds with other factions in the City. However, they are otherwise quite willing to peacefully coexist with others, so long as they are willing to regularly cede art and meaning to the Modrons to be destroyed. Knowing that there is non-ephemeral art out there lying — and to a modron, all art lies — seems to offend the modron to its very nature.

In contrast to their attitude towards the written word and statuary, once they’ve defaced any meaning from the art, they defend the structure, stability, and architecture of the city valiantly. In many locations, modrons prune back weeds, repair damage from water, or create new aquaducts to better inhabit the city. Many believe the modrons to be the original builders of the City, but sages retort that the City grows, whether modrons work at it or not. 

There are reports of modrons manufactured of non-native materials like brass and cherrywood; those are reportedly cheerier and much friendlier towards non-modrons. Their hierarchy is unclear, but simpler figures respect more complex figures; the more complex figures in turn seem more capable than the simpler ones.

Gith. Gith are the most frequent humanoid inhabitants of the City. They tell tale of generations of slavery on the wormworlds, under the thumb of illithids; their founding hero Gith fought them free and the race named themselves after her. After finding escape in The City they destroyed the gateway through which they fled, and formed a schism between The Faithful of Gith (Githzerai), who held this act of desecration was unforgivable, and the Children of Gith (Githyanki), who place no special religious faith in the place they found themselves. The two types of gith are violently opposed to one another, uniting only when faced by incursions of their former masters such as illithid or slaadi.

Githzerai. The monastic settlements of the githzerai often occur far from any gates, or near dangerous or undesirable gates. They subsist on gardens which they grow in the City using water from fountains which they clarify alchemically and plants grown in the strange light of white walls. They spend their time in toil, exploration, contemplation and prayer. Their strange religion seeks the source of all things; to understand the order of events which occurred in the many worlds (Chronos) and the order of events which occurred in the City (Kairos). They are opposed to the modrons particularly, who destroy the Sacred City. They are also frequently encountered in the “gardens” of their monasteries which lie in Limbo, as they find the contrast allows them better able to concentrate — and some say, to shape the growth of the City in turn. 

Githyanki. The piratical Githyanki, on the other hand, devote themselves to war-like pursuits. They raid the City for materials, locate and analyze gates, and then raid the other side of the gate for what they can seize. They establish dominions, build fortresses, and tunnel through walls. Much of what is known about mining in the City comes through them. Their largest settlement remains Tu’narath, the place through which the Gith first made their redoubt when fleeing the illithid, and which now opens onto that dead world. They use the architecture and art of the City to locate new gates through which to make war or to sell their ill-gotten booty.

Tieflings & Hell. As Hell is the largest and most sophisticated consortium of worlds, it would be odd if they did not have a presence in the city. And, indeed, representatives of the Iron City began an incursion into the Endless City in a now-forgotten age. Dis claims this act to be a reconquest; that the City originated as did Hell with the first free-willed being’s home, and that all of the City is theirs by right. However, they also aggressively seal gates leading from their worlds into the City (under the guise of operational security), and react poorly towards gifts of materials from the City.

Minotaur. Nobody’s quite sure how it happened, but there are a whole bunch of bull-headed guys wandering around The City. They come from a variety of worlds, they generally have little magical ability themselves, and they are uniformly male (though breed true when the opportunity presents itself). Somehow, however, they all seem to know each other, and find themselves drawn to the City. Many tinker-style traveling merchants are minotaurs, traveling in the City from gate-town to gate-town, selling their wares.

Archmages. For some reason, archmages from a dozen worlds really enjoy the cosmopolitan nature of the City. Maintaining a presence of some sort here is practically on the archmage final exam. Liches, mummies, and other undead creatures made out of former mortals now clinging to power also make up this class.

Priests & pilgrims. A place which duplicates the works of man is like catnip to a godbotherer. Many, many religions hold the City to be a sacred place, worthy of at least a pilgrimage. As otherworlds go, its conditions are sufficiently similar to Material worlds that visitors need only ensure the gate they use is safe. Frequently an abandoned gate will be the haunt of an angel, naga, sphinx, or lamassu, left behind to guard the space until pilgrims use it once again. The pilgrims who are encountered in the City are visitors and tourists, and generally overpay for a trinket which will not age well back in the World.

The Lady of Pain. A floating porcelain-masked figure, or perhaps race of figures, made of silk and steel. The City shapes itself as she wills it, her shadow flays by touch, and she frequently teaches a lesson by banishment via teleportation into a random labyrinthine segment of the City. She punishes particularly those whose actions too-radically affect the city: it seems that the expansionist modron and the reconstructivist githyanki do not try her patience, but the Temple of Aoskar for whatever reason did, and that lesson isn’t lost on the powerful: groups which attract her attention may be destroyed in a heartbeat, with no warning.

Our planescape-like factions are going to be, again, stolen straight from Patrick’s article.

Academicians: “The City teaches us who we are”. The academicians are the most powerful and popular faction, because they uphold the status quo of the City, such as it is. Their actual interests are strongly divided; between Contextualists (who seek to understand the events on which the city bases itself, using near-historical events to understand true ones), Counter-counters (who reject all counterfactual evidence as irrevocably tainted), the Stylists (who ignore truth in favor of beauty) and the Originalists (who seek the seeds of events in the city for their own sake). In all cases, their relationship with The City is, well, academic: they publish papers and vie for respect within their organization. The Academy’s store of knowledge produuces maps, gate-keys, supplies of trade goods, and of course security for expeditions deep into the City. The Academy is based out of the gate-town of the same name, which shares a triple-gate to the City of Brass, the Iron City, and the so-called Bright City of Hestavar

Alienists: “The City is bounded by Outside”. A splinter group of counter-counters who engage with the city as a dangerous foe, the alienists are adventurers who seek personal fame, generally by trying to explore the edges of the City. They’re the source of rumors about Outside, strange creatures tied to no known world. The fame and fortune they seek is driven by artifacts they can bring back from the edge, showing un-City-like influences, new worlds, or similarly shocking news. The alienists are based in the City of Brass, where the cosmopolitan Efreeti are intrigued by their ideas.

Anarchist League: “The City was ours, and we’ll kill you and take your stuff!”. A popular faction of bandits and thieves, the Sodkillers oppose the Harmonium on the basis of a war back on Ortho — the Sodkillers claim to be the true descendents, pushed back from their gate towns by the following invaders of the Harmonium. They’re a sort of rebel-alliance which opposes the Harmonium in particular, but any sort of central rule in general. They have no central base, but can frequently be found sheltered in gith settlements, finding favor in their loose structure.

Athar: “It’s just another place, you know?”. The faithless are based out of the Iron City, and hold that the City has some interesting properties, but it just isn’t that improtant; they oppose the Academy because the academy’s entire goal is based on ignoring the Worlds in favor of the City. Their sponsorship by the trade consortia of various unsavory planar powers (the Iron City particularly) has led to them being considered somewhat unsavory.

Believers of the Source: “The City was started at the first moment of creation”. The believers hold that the City is in fact related to the demiurge, though are divided over what to do with this fact. They work out of the gate-town of The Foot of the Throne, a famous pilgrimage site with a gate to Celestia. Some believe the City to be itself holy, and thus only to be visited by the shriven (Godsmen); others, that none can be suitably shriven but that the City will forgive (the Bleak Cabal), and yet a third faction that the previous two are both correct, and so everyone who has visited the City and then chosen to leave (without intending to return) is guilty of a great sin (Anti-revolutionists). Central to all three groups is the search for the Throne, the center of the City.

Cynics: “The City is chaos”. The cynics believe that there is order in chaos, but a surface understanding leaves one unable to see it, and that the City in particular has a many-layered approach to truth which can be difficult to perceive. They are often difficult to predict, erratic, and intuitive. They control Arsanith, a githzerai-controlled gate-town, but can be found in many other gate-towns as well, because their teachings are tempting to the powerless.

Doomguard: “All things fail; the City before us”. The Doomguard, from the Citadel Exhalus is the Nether, seek to cause gates to the city to swallow the area into which they open. They believe if they can cascade enough property into the City, its danger to the other worlds will be at an end. There is some evidence they may be correct.

Fated: “The rich resources of the City belong to who can hold them”. The Heartless are a primarily human faction driven by amoral observation of fact. From their gate-towns of Columbia, Fountainhead, and now-flooded Rapture, their agents see what they can get. Other than those gate towns, the city-state of the Fated isn’t expansionistic (they’re nervous about what they actually can hold!), and tends to favor proselytization beyond their own borders.

Harmonium: “The City is an obvious extension of Ancient Harmonia”. A former nationalistic polity whose gate was lost to modron expansionism, their secondary gate-town of New Harmonia (opening onto a stretch of idyllic world called Ortho) has made peace with the modron border. They’re a fundamentalist, authoritarian bunch.

Sensates: “The City is great! Where else can you get Dothraki takeout at 3 AM?”. The hedonistic (and materialistic) sensates seek to take advantage of the juxtaposition of cultures which the city creates or, if further along that particular path, exploit the actual edges of the city, mining them for new experiences and treasure. Their materialistic ways make them an enemy of the Academy and gives them a complex relationship with the gith. They are based out of the Festhall, a gate-town to Azzagrat.


Ghostly Haunt

Consider a haunted house. There is the sense of the place itself acting against intruders and supporting its own allies; doors slamming, windows becoming gates to other worlds, messages on mirrors. Maybe ALL WORK AND NO PLAY MAKES JACK A DULL BOY, and characters enter the madness of the place; perhaps apparitions show themselves and characters are misled in that way. Perhaps objects animate, or cold spots enervate, or someone is crushed by a falling chandelier.

Some of this is due to the haunt’s association with a whole pack of ghosts. It seems that the tragedies of such a location tend to accrue, and where originally it was simply a violated burial ground, it swiftly becomes a site of a grisly murder, and then perhaps a tragedy murder-suicide, and then perhaps a serial-killer’s staking ground. By the time the latest victim arrives, it’s a wonder they can find a spare bedroom amongst the ghostly throng!

The tools to enable this are simple: the possession ability of ghosts is our baseline. I might replace the ghost’s ghastly visage with a dreadful moan (substituting a mummy’s paralysis for the ghost’s aging effect, and sound for sight) in such a world, since the ghost will never be seen (it’s a haunter). Of course, we will also use specters and their poltergeist variant heavily. The ghost is the centerpoint, though: it can move from room to room, and possess objects (causing them to animate per animate object). When it animates the room itself, it can slam apertures and fling small objects, but it still has to more or less obey the logic of the structure.

Such a ghost will need lair actions, of course; that’s where the rest of the supernatural effects will come from.

Ghostly Haunt
Medium undead, any alignment
Armor Class
14 (magical armor)
Hit Points
72 (16d8)
Speed
0 ft., fly 40 ft. It can hover.
STR(-2) DEX(+1) CON(+0) INT(+0) WIS(+1) CHA(+3)
Damage Resistances acid, fire, lightning, thunder, bludgeoning, piercing, and slashing from nonmagical weapons
Damage Immunities
cold, necrotic, poison
Condition Immunities
charmed, exhaustion, frightened, grappled, paralyzed, petrified, poisoned, prone, restrained
Senses
darkvision 60 ft., passive Perception 11
Languages
any languages it knew in life
Challenge
8 (3,900 XP) (9 in lair; 5,000 XP)


Ethereal Sight.
The ghost can see 60 ft. into the Ethereal Plane when it is on the Material Plane, and vice versa.
Incorporeal Movement. The ghost can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.
Invisibility. The ghost is invisible.
Rejuvenation. As long as the ghost’s lair still exists, it will reappear in the lair 24 hours after being destroyed. This can be prevented via barring extradimensional access to the lair (such as via forbiddance or hallow), by resolving the ghost’s reason for continued existence, or by substantially destroying the lair in the ghost’s absence.
Legendary Resistance (3/Day). If the ghost fails a saving throw, it can choose to succeed instead.

Actions
Withering Touch. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 17 (4d6 + 3) necrotic damage.
Etherealness. The ghost enters the Ethereal Plane from the Material Plane, or vice versa.
Possession (Recharge 6). One humanoid that the ghost can see within 5 ft. of it must succeed on a DC 14 Charisma saving throw or be possessed by the ghost; the ghost then disappears, and the target is incapacitated and loses control of its body. The ghost now controls the body but doesn’t deprive the target of awareness. The ghost can’t be targeted by any attack, spell, or other effect, except ones that turn undead, and it retains its alignment, Intelligence, Wisdom, Charisma, and immunity to being charmed and frightened. It otherwise uses the possessed target’s statistics, but doesn’t gain access to the target’s knowledge, class features, or proficiencies.
The possession lasts until the body drops to 0 hit points, the ghost ends it as a bonus action, or the ghost is turned or forced out by an effect like the dispel evil and good spell. When the possession ends, the ghost reappears in an unoccupied space within 5 ft. of the body. The target is immune to this ghost’s Possession for 24 hours after succeeding on the saving throw or after the possession ends.

Legendary Actions
The ghost can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature’s turn. The ghost regains spent legendary actions at the start of its turn.

Withering Touch (2 actions, not while possessing). The ghost uses Withering Touch.
Etherealness (not while possessing). As long as the ghost is not in (or entering) an area of daylight, the ghost uses Etherealness.
Melee attack (only while possessing). The ghost makes a melee attack.
Glide. The ghost moves its speed without provoking opportunity attacks.

Lair Actions
On initiative count 20 (losing initiative ties), the ghost takes a lair action to cause one of the following effects; the ghost can’t use the same effect two rounds in a row:

  • A magical mournful wail fills the lair. All creatures within 60 feet of the ghost who can hear the wail must succeed on a DC 14 Wisdom saving throw or be frightened of the lair for 1 minute and flee it. A frightened creature can repeat this saving throw at the end of each of their turns, with disadvantage if they can still see the lair. After a creature is no longer frightened by this effect, they re immune to it for 24 hours.
  • Objects in the area magically animate. The ghost casts animate objects with no components and with a duration of 1 minute (instead of concentration), and with only 7 creatures-worth of value (instead of 10). If this ability is used for a second time, the previous casting ends.
  • The area is filled with images important to the ghost. The ghost casts major image with no components and with a duration of 10 minutes (instead of concentration). If this ability is used for a second time, any previous casting ends.

Regional Effects
The region containing a legendary ghost haunt’s lair is warped by the ghost’s magic, which creates one or more of the following effects:

  • Bad weather is common within 6 miles of the haunted site, with impossible weather phenomena (stationary spiraling clouds) common.
  • Those who sleep within 1 mile of the haunted site have dreams shaped by the ghost; spell slots cannot be regained at the end of a long rest within that area unless the ghost allows it.
  • The violence and tragedy which surrounds the ghost weakens the Material Plane. Fissures to the lands of the dead or to fiendish planes allow creatures native to those places to dwell nearby.

If the ghost is destroyed, these effects fade over the course of 1d10 days.
Lemmee just say this: Legendary creatures’ stat blocks are a pain in the rump. That is all.


Fatigue and Moods

D&D has the Exhaustion scale, which lots of systems hook into; you know,
Exhaustion 1: Disadvantage on checks
Exhaustion 2: Speed halved
Exhaustion 3: Disadvantage on attacks and saves
Exhaustion 4: Hit point maximum halved
Exhaustion 5: Speed 0
Exhaustion 6: Death

You get exhaustion when things go against you; you lose exhaustion when you can long rest (or if you can catch a greater restoration or a potion of vitality).

We’re missing some other, lesser versions of fatigue, though: let’s call them moods. These are conditions (like charmed).

Angry: While angry, you don’t consider others your allies, you have disadvantage on ability checks (except for strength checks), and attack rolls against you have advantage.

Sad: While sad, others don’t consider you their ally, you have disadvantage on ability checks (except for dexterity checks), and your attack rolls have disadvantage.
Lonely: While lonely, you have disadvantage on saving throws against being charmed, and succeeding on a saving throw against being charmed cannot give you immunity to being charmed. Elves cannot become lonely.
Anxious: While anxious, you have disadvantage on saving throws against being frightened, and succeeding on a saving throw against being frightened cannot give you immunity to being frightened. Halflings cannot become anxious.
Gloomy: While gloomy, you are vulnerable to necrotic damage and have disadvantage on saving throws against necrotic damage. Whenever you fail an attack or check by more than 5, you cannot take reactions or multiattack, and can take only an action or bonus action until the next end of your turn.

Queasy: While queasy, you are vulnerable to poison damage, and have disadvantage on saving throws against poison and being poisoned. Dwarves cannot become queasy.
Fragile: While fragile, you are vulnerable to bludgeoning, piercing, and slashing damage, and attacks against you have advantage.

Shocked: While shocked, you are vulnerable to acid, cold, fire, lightning and thunder damage, and your saving throws against these damage types have disadvantage.
Of course, then we need the more positive ones. Things like:

Hopeful: Your current and maximum hit points increase by 5.

Brave: You have advantage on saving throws against frightened.

Confident: You have advantage on saving throws against charmed.

I’m inclined to let calm emotions affect all of these; I’m also inclined to let an ally counselor you out of them with a campfire scene. Have a negative one and try to sleep on it? Probably turns into a point of exhaustion.
These would make excellent outcomes for, like, long term travel hazards.


Improving Monsters

Reminder: leader monsters are +40 hp, +2 to d20-scaled things, and it deals 20 more damage per round (via an additional attack, or a few more points on each attack if it’s already got multiattack). Easy-peasy; makes the numbers all bigger. Doesn’t do a lot for outside-the-numbers

There’s other dimensions in which to improve monsters, of course. I recently ran an adventure with a wizard’s college which had been infested by a spirit of chaos, a death slaad with a few additional spells and lots of planning. That one relied on granting the monster a panoply of ritual-like spells to be used solely off-screen: it already had the ability to assume humanoid form, but it also had animate dead, magic mouthNystul’s magic aura and planar binding. Not really combat spells; specially chosen to do maximum damage in my particular. These don’t affect the CR. If anything, these are just adventure seeds; knowing that there’s a monster dropping major images here and there would work with any monster type, using a wand if it’s not in the stat block.

So that’s one dimension: plot power. Raising an army or dissolving a mob, showing an outsized set of mental stats and knowing secrets. When NPCs influence NPCs and reveal plot secrets, the details aren’t that important; if the DM says the Blod-Prinzl is the Chosen One of the Giants, it doesn’t take a stat block saying “charms giants by the thousand”. But it might say that in the adventure notes, of course!

Similarly, “increases yearly food production four-fold within 5 miles”. Of course a powerful druid moving in would have such an effect, but we hide that they would do this in the description of the plant growth spell and assume they cast it in their down time. But what about “prevents facial boils” or “eases childbirth”? Or “increases the fluctuations of lit fires” or “calls storms”.

These can engage in rules systems, of course: Food is a thing that matters, childbirth can kill, fires get lit around characters, and storms affect all sorts of parts of adventuring. Those turn into adventure elements which do need statistics; during a storm, there’s heavily obscured spaces from the rain and suppressed fires. The called up army will of course be guards, and they will be charmed, and those are both things game rules can affect.

But all together, you don’t modify the leader to make that happen per-se, you just write it into the adventure. There is an illusion here, there is a passwall there. The source of these things should be suitably impressive, but you don’t necessarily need a new block for that.

High level adventurers don’t necessarily kill monsters by numbering them to death. More precisely, by the time they’re numbering the monster to death, they’ve already trapped the monster (so that it’s subject to their mighty math) and may have ensured they themselves are untouched by the monster’s strength. For instance, flying wizards raining down fireballs against a stone giant: it’s expensive, but what’s the giant gonna do? Run away under cover ideally, of course. Encounter over. But maybe the payload’s an enlarged hasted action-surged multiattacking  fighter with a flaming sword; maybe it’s an ethereal assassin. Whatever. The point is, math is half the problem, but it quickly approaches problems of engagement; speed, range, weapon immunity, and just straight up action economy.

The weapon immunity really hurts high level monsters. In previous editions, there was a ladder of magical weapons; +1 can harm elementals, but it takes +5 to hit a balor. That’s gone now, so that there’s no longer a system in the game which privileges items with plusses. There’s a trivial fix for that: a monster with protection from weapons can only be harmed with a magical weapon whose rarity equals proficiency. This will of course affect martial characters to a certain degree, but the really big effect is to make big scary monsters more expensive to attack for groups arming soldiers; even magic arrows would get pretty costly. Worldbuilding.

But even with that, there are some monsters without ranged attacks and no flight. Those monsters are dead meat. There are monsters with no ability to shut down spells, low wisdom scores, and the humanoid type. They’re dropping to a charm-type spell at its earliest opportunity, and probably joining the party to boot. Maybe the monster can’t see invisible, has no area attacks, and can be stabbed; not a problem for low-ish challenges, but it couldn’t be a Big Bad at challenge 20; it’s gonna die.

Those problems also need to be attacked. The problem isn’t math; it’s action economy, it’s mobility, it’s range. The simple solution is to make the creature legendary (move, perceive, attack as actions), give it the legendary defenses, ensure it can climb, jump, or fly. It’s still getting forcecaged, though; it’s still getting planeshifted away from, it’s still getting wall of stoned. Those are a little harder to lock down; most monsters are vulnerable to them. I think your best solution in general to that kind of lockdown is an ally with dispel magic, or some element of setting design which lets martials invoke dispel magic.


Planes and Worlds

I’ve posted a few times on the planes of my campaign as I firmed up exactly what cosmological model I wanted (seems to be something going around; while this was sitting in my drafts, enworld had this and rpg.net had this).

I’ve been thinking about the distinction between a layer and a plane. “Layer” is just a way of breaking up the monotony of a generic location into actual adventurable locales; the Abyss is the plane of all the demons, but the three layers of Azzagrat are specific environs (under the control of Graz’zt). Other than the Abyss, D&D planes are classically made of a fixed number of physically concrete layers; the Seven Heavens contain seven layers, one per heaven-mountain. Cool and all; not what I’m into.

Here’s what I’m into:

Let’s start with the base concept of a Domain. Domains are locations which exist; they have borders. There’s Cathule (where my game is set), but also Barovia; Dis (my first layer of Hell) can be sailed to from Cathule but literally is in Hell, Graz’zt’s layer of Azzagrat, and so forth. The borders of a domain set the limits for things like teleportation and scrying; all points in Barovia are in Cathule and so can be scried, but not the other way around.

Domains organize into Realms. Realms can be defined by anything — Hell is a Realm, but the country of Dis and each of the worlds of Baator and each of the worlds of Naraka and of Purgatory and so forth, those are Realms. Sometimes the borders between two domains in the same realm are very soft, such that you can walk or sail between them (such as Cathule to Barovia, though not the other way around) and sometimes very hard (such as the various realms of the Abyss). Still, some form of transport is generally achievable, through the use of gates at a minimum.

Okay, so: No structure, I get to draw a line diagram. As long as the plane shift spell exists, does any of this matter? Yes-ish. In the same way I draw a campaign map even though we’re just going to skip over most travel montages, I should do the same thing for planar campaigns. In the same way the characters will pick between a coastal cog and the inland caravan, I should provide the Charonic Nether Skiff versus the Limbic Stormwalk. That’s where the “planes” of the Nether and Limbo start to matter: they’re really big Realms with not much content that exist to fill maps: they’re basically oceans, to the Realms’ islands, including such weird effects as “the sun rises in the east” under the similar-behavior “the dead wind up in the Nether”. Most of the time, you don’t have an adventure on the open ocean, you have it near a feature: in a realm.

Neat. But humans don’t work that way; they organize orreries and seating charts. So probably the Realms get called planes and hooked up in a big wheel, nice and far away from the infinite expanse of empty air called the Inner Plane of Air. But don’t be fooled: that’s the equivalent of a blank spot on a map or a barren rock covered with gull poop until some adventure comes along and needs it, making it concrete.