We all know that Hell bargains for souls: they’re the lawful-evil bureaucratic fiends who seek the degradation and subversion of mortals. They’re Milton’s Children, they’re a 90’s-style coke-fueled law firm that never ends, they’re Kafka’s Nightmare.
But what is the soul? Why do they want them? Do they treat them as wealth, and if so, do they hoard them or invest them or what?
D&D’s answer has traditionally been super literal. When you die, there is a mysterious process, but the ineffable thing that was you travels to — or awakens in — the Outer Planar realm which matches you two-axis personality type as a new creature, a Petitioner. The “petitioners” of some of the lower planes are larvae, soul-worms, much sought after. Others are as they appeared in life, or animals, or unformed light. In 4e, there was some transport involved, so there were adventures to restore the spiritual roads along which souls reached their makers, piratical demons, etc. In the forgotten realms, if you try to be tricky (“no gods for me!”), you wind up entombed in the Wall of the Faithless for eternity. In Planescape, you change mailing address (since you’re bopping around the planes already!). The Devil/Demon Blood War needs troops, so evil souls get sent into that fray as low level gribblies. The Upper Planes seek to escape the endless cycle of conflict (sit down, Ysgard, nobody’s talking about you); they collect petitioners for the good of the petitioner.
An aside: in earlier editions of the game, you could not raise dead an elf: they didn’t have souls. That was in the rules text. We lost that in 3e (I think it was still present in 2e?), to our detriment. Why can’t you charm an elf? Because charms enchant the soul, and elves are invalid targets; they’re P-Zombies, distinguished as such due to deific intercession. I guess technically we still have that in 5e if I hold fast that elves are mortal Sidheelien, that latter of type fey, fully invalid targets for that spell. In the 3e setting Ghostwalk, elves don’t leave spirits behind, but enter the grove of spirit trees.
The features of this rubric are straightforward: while there isn’t mechanical heft behind it, souls are concrete objects which can be seized and traded and held. They’re post-mortem artifacts, and don’t have a lot of consciousness in them. They power things through the power of plot.
I don’t really like this view of the soul as it regards the motivations for the powers of Hell. It’s gameable, don’t get me wrong, but it puts a concrete understanding on the ineffable. Why would any power want a stake in an individual mortal’s soul if ultimately souls are a commodity, tradeable by the bushel? Even granting that they might come in different grades, there is a physical object associated with the soul (the petitioner), so there’s some concrete value attached there. There’s an upper limit to their worth. And I find it difficult to build a post-mortem economy that allows Faustian bargains when most souls are, well, at the level of Faust’s. The power the Ruinous Powers bestow has to be so cheap for them to make it worth it that I don’t really know what to do with this.
I say that Hell is the CIA, and the soul is a pork-belly future (to propose two metaphors simultaneously). What I mean is that a Faustian bargain is not to harvest ectoplasmic phlegm or a soul-larva, but instead, for the deeds which a living character with that power will do while they are alive. Or undead. First, Hell has aims in the mortal realms. Secondly, the disaffected or the corrupt both will weaken the status quo, so make tempting prospects. Thirdly, Hell has an enormous armory: staves of fireballs for rebellious lords or hats of disguise for ambitious courteseans, it has programmed illusions and incubus handlers to blunt those who might otherwise grow on their own to lead nations, or philtres of love or arrows of slaying to give to ones adversaries to tip scales against a hero. A Faustian Bargain is not really about selling one’s “soul” for power; it’s about accepting power and the guidance that comes with it, and striking for one’s desires using underhanded mechanisms. This is a dangerous road because the power is addictive, and the fact that it’s being offered implies the direction it’s being applied agrees with Hell’s aims.
Like a staff of fireballs, a warlock investment (or clerical investment, or paladinical temptation, or whatever) is given unto its recipient and then the transaction is over. It’s one of the easiest Faustian bargains to strike, really, since in my view a supernal character is made via a transcendant experience: if a warlord beholds an angel in the field of battle, they’re quite likely to convert their hit dice to cleric. The ruinous powers get to do the same thing.
How does your mid-level Diabolic Actuary ensure that this is the right deal to strike, that this podunk peasant could do some real damage before the inquisition catches up? Dirty pool; the augury spell can be combined with the bureacracy of Hell to remarkable effect. Assume Satan (like the Big Guy) marketh e’en the sparrow’s fall; assume also that when the Prince of Darkness marketh something, it stays damn well markethed. Then since the punishment/reward cycle for deviled eggheads is so tight, the actuary can simply ask “How will making this deal wind up for me“, a perfectly valid augury question, and get an immediate response. To make this work, of course, the Dread Lord has to have a very immediate personal touch on His accountants. But that seems very reasonable too; they report back to the Head Office after every deal or something.
I mentioned the inquisition. Sure. If there is a CIA, there has got to be an MI5 (or whatever, since they’re not really opposed. Stasi, but for the angels. Boy, this is getting tortured). The thing about the forces of good is that they feel responsible for their actions. The angels do not hand out heavy munitions at will, because that is what makes them angels; as a result, those they have entrusted with heavy munitions are well-organized and on-mission. That mission is “end the undue influence of Hell”, but it can’t go so far as “cut off all contact with Hell” because humanity is neutral; all-out opposition would become all-out war. That kind of battle would trigger the end times.
But then, I mentioned a Prince of Darkness with enough foresight to bootstrap augury into a Turing-complete prognosticator. Which means that any such outbreak of hostilities has already been seen (“Knowing the price of failure, if I were to propose the following End Times plan, WEAL or WOE: …”). Which means that triggering Armageddon is probably a positive for the Angels (or else Satan would already have pulled the switch, but not so positive that they see the way out of that end-times battle. Factions of angels probably do argue in favor of the End Game, because of this very logic (The Fallibility of Evil faction). But others take a more measured approach, hypothesizing mutual annihilation and infinite suffering (the Covenant faction). Still others look to the younger races, hoping that they will find a solution to this dilemma, while remaining fundamentally captive to their duty as caregivers and wardens (the Taurielline Faction; Undertale, eat your heart out).
But this is D&D; if there’s a synonym for spirit in this game, it’s got a monster manual entry. So of course when you die there’s a spooky ghost left behind, and of course angels and valkyries and demons and Anubis and Odin and Satan and Buddha fight over the remains. But on the cosmic scale, its value is that it was once sentient and irreplacable and you; monsters eat it or make hats out of it in the way that they eat human flesh and paint themselves in the gore. You can power a water wheel with a soul, or make a wraith or specter (or lantern archon or einjariar), but the reason they’re valuable is as boots or as brains, or for their own sake, as of a flower.