D&D 5e doesn’t have a lot of good low-ish level spellcastery undead, which is annoying for a game which involves a fair bit of grave defilement.
There’s the Lich. Strikes fear into everyone’s heart. Has spells. Has achieved the pinnacle of undeath. They’re CR 20, so for my purposes might as well not exist.
There’s the vampiric spellcaster. Vampires are too precious for me to use here: they’re specific individuals, romantic/monstrous figures, with a weird quasi-biology. They’re not the sort who sit around in mouldering tombs waiting, they’re the sort who actively go out and bother heroes. That said, this is a great option to remember I have and to come back to, because they’re otherwise just right.
There’s the mummy lord. Actually, this is pretty good as a “sits in tomb but isn’t a Lich”. Swap the spells out, maybe (maybe!) strike the desert specializations to make them match the kind of wizard I’m using them as, and this is a good option. They’re still CR 15, which is a little steep for my taste, but in the realm of doable.
But then: silence. Let’s fix that! Our needs are simple: some spellcaster-types for a good mix of undead types: Ghoul, Wight, Specter, Mummy, Wraith.
I left a bunch of undead types out, either for seeming too mindless to me (a lot of undead have low intelligences but I think that’s just being chauvinistic for, say, ghouls; others like zombies really are just too dumb to still be mages). There’s space for more-magical shadows and zombies, it’s just not in the same space I’m talking about a crypt-bound wizard-type. Save it for the crypt-bound sorcerer or warlock-type “flaming skeleton”. That’ll be a great article.
So our target is the Ghoul-Mage, the Wight-Mage, the Specter-Mage, the Mummy-Mage and the Wraith-Mage.
Ghulmage (CR 5)
The eaters of the dead are those warlocks who trafficked with unclean spirits sufficient that they slid into a maddened undeath without even noticing. They combine the spellcasting abilities of a 7th level warlock (so: a 2 4th level slots of: Blight (1 living target 30 feet 8d8necro, con save half), Polymorph; 3rd level Bestow Curse, Fear, Lightning bolt, 2nd level Detect Thoughts, Invisibility; cantrips Chill Touch (2d8), Minor Illusion, Silent Image at will?) with the traits of a ghast and hit points appropriate to their station.
I think I’d throw a “eat a corpse/regain a spell and some hit points” thing on them too, just to be super cruel, but that’s just me, and wouldn’t come up all that much. I would also say that a ghulmage is a way to become powerful: they just transition into normal ghouls if they don’t have the oomph to make it in the CR 5 leagues.
Dead Witch (Lesser: CR 3 Greater: CR 7)
A wight arises when a powerful knight is suffused with the energies of the undead and comes (cackling!) back to life, often with dark forces or blood oaths invoked. Dead witches are similar: the corpse of a spellcaster with a dark force animating it. The lesser form are as wights but as, say, 3rd level casters (acid arrow, magic missile, burning hands?). The greater form are mages which transitioned into wighthood (spells per NPC mage). In both cases, I suspect they have a familiar flitting around the battlefield which is what they generally use to life drain: they cast a cantrip and the familiar does a life drain touch.
Phantasm (CR 5)
The wizard’s skill without the wizard, a phantasm is an obsessive echo of their goals. It’s effectively a beefed up specter, spells etc, with a “favorite” set of spells which it may cast renewably. I kind of like 2nd level spells for this: this is the same CR as a wraith, a red slaad or a troll, so something like “all the scorching ray you can eat” or “ray of enfeeblement look I’m a ranged shadow almost” or the mean ones like “suggestion” all seem fine. Fireball every round feels wrong, though, so 3rd level is too high. Magic missile (remember, at 2nd level!) Phantasms seem particularly fun in a 4d4+4 damage per round kind of way.
Any similarity between Phantasms and the Wizrobe from Legend of Zelda is purely coincidental.
Embalmed One (CR 7)
The point of a mummy is to live on after death, and wizards and sorcerers seek that immortality the same as princes and priests do. The downside is that the rituals a mummy goes through in order to secure their immortality occur after death, and so lie in the hands of assistants and underlings — or, perhaps worse, in the hands of the wizard’s masters. An Embalmed One is a pet wizard, their vital organs in a jar, forced to obey the holder of the jar. Otherwise as a mummy with the hit points for CR 7 and the spells of an 11th level mage (or, as I prefer, warlock: 3 slots of 6th level: Disintegrate, Globe of Invulnerability; 5th level: Cloudkill, Telekinesis; 4th level: Banishment, Stone Shape; 3rd level: Blink, Dispel Magic; 2nd level: Spider Climb, Web; 1st level: Magic Missile, Detect Magic; cantrips: Ray of Frost, Shocking Grasp).
Whoever holds the canopic jar can command the Embalmed One absolutely; an embalmed one in possession of its own canopic jar may either keep the status quo or destroy it, which will eventually reduce it over time to a mere mummy.
Spellwraith (CR 9)
One of the more feared forms of immortal enemy, a wraith with spellcasting powers is a terrifying foe. Worse, spellwraiths retain their human intelligence; they cast as level 13 casters, giving them 3 7th level slots of 7: Reverse Gravity and Finger of Death, 6: Wall of Ice and Flesh to Stone, 5: Telekinesis and Dominate Persion, 4: Ice Storm and Dimension Door, 3: Sleet Storm and Lightning Bolt, 2: Scorching Ray and Darkness, 1: Magic Missile and Sleep; Chill Touch, Ray of Frost and Mage Hand.
I think I’d let them walk through people as part of an attack.
Now, to actually stat these up!