Dealing with Fiends

[Desril]

So 5e doesn't really have rules for making deals with demons and devils, but they're a major part of fiction, so how would you go about doing it?

If someone made a deal with a demon, freeing it for power, would they gain a level immediately, but needing it to be a Fiend patron Warlock? Would they gain Pact Magic as a class feature regardless of their class? Or maybe Rage? An Invocation? A Charm is much too weak, but Blessings are supposed to be the work of Gods, not mid-level demons. Would any of those be unbalancing? Once said bargain was struck, could the demon revoke the power granted?

[Unoriginal]

So 5e doesn't really have rules for making deals with demons and devils, but they're a major part of fiction, so how would you go about doing it?

It's discussed in the books, though.



If someone made a deal with a demon, freeing it for power, would they gain a level immediately, but needing it to be a Fiend patron Warlock?

Nope, a Demon has no reason to honor their deal once freed. So it would be entirely up to the Demon if they respect it.

If you meant a Devil, then still no. However, a sufficiently powerful and knowledgeable Devil (or Demon who has decided to actually do you the favor) could teach the person who freed them in order to allow them to take into Warlock (if the person meets the requirements in case of multiclass) the next time they gain a level (or when they earn their first level if this is a Warlock's backstory."



Would they gain Pact Magic as a class feature regardless of their class? Or maybe Rage? An Invocation?

Fiends are not usually able to give that kind of things. But a DM could decide this particular fiend can, but it'd need to be a pretty high level one.




A Charm is much too weak

Not really, no. The DMG indicates its the kind of thing you can expect from creatures of the level of an ancient gold dragon or from finding an archmage's secret, so it would be appropriate for a Fiend to give it.



but Blessings are supposed to be the work of Gods, not mid-level demons.

Some of the most powerful fiends are gods. But a mid-level demon doesn't really have the power to give anything like that.

A low or mid level Fiend can offer their service for a time, any riches or magic items they own, information, their influence in dealing with more powerful fiends or with mortals they know, or the like.


Would any of those be unbalancing?

A Charm or a Blessing wouldn't, unless designed to be über-powerful


Once said bargain was struck, could the demon revoke the power granted?

A Demon could, yes. A Devil would have to respect the terms of the contract (so if the contract allows them to revoke the power, they can, otherwise they can't).

Note that in case of a Warlock's Pact the entity cannot remove what you have learned (so you don't lose your levels), but your Patron could decide to not empower you anymore/stop teaching you, meaning you'd need to find a new Patron.

[Naanomi]

Historically there is 'ritual magic' that can 'force' a demon (or daemon for that matter) into agreeing to the terms of a struck bargain; they just don't tend to like it much and actively look for ways to subvert the 'deal' when compared to the same thing with devils.

Especially on the level of Demon Princes and the like you'll find demons that (although still 'capital C' chaotic) are into pacts and plans and creating disciples (Grazzt, Dagon, Orcus, and Pazuzu most commonly; but others as well) that might have them ending up as Warlock Patrons (or refluffing other classes to fit that idea; I like the idea of Barbarian powers being 'granted' as a very angry and physical Warlock-style Pact).

Some few are actually Gods as well as Demon Princes (Lolth, Vaprak, The Great Mother; sometimes others like Sess'inek) that can be both a Warlock Patron and have Clerics

[Unoriginal]

Historically there is 'ritual magic' that can 'force' a demon (or daemon for that matter) into agreeing to the terms of a struck bargain; they just don't tend to like it much and actively look for ways to subvert the 'deal' when compared to the same thing with devils.

There was also books like the Goetia that indicates how to use God's power to invoke demons and have them serve you.


Some few are actually Gods as well as Demon Princes (Lolth, Vaprak, The Great Mother; sometimes others like Sess'inek) that can be both a Warlock Patron and have Clerics

Also Orcus.

[Naanomi]

Also Orcus.
Orcus wants to be a God, and succeeded for a while via his Tenebrous plot; but I don't think he actually is one at the moment. I could be wrong

[Unoriginal]

Orcus wants to be a God, and succeeded for a while via his Tenebrous plot; but I don't think he actually is one at the moment. I could be wrong

You're right, he's never called a God in 5e, even if he has worshipers.

[Tanarii]

What you do is hang out with them regularly, have their back, and realize your stupid fights are stupid and be cool after.

Oh wait. You said 'Fiends'.

Fiend Deals can result in anything the DM is willing to give. But if it's for magical powers, just multiclass as an Achfiend Warlock next time you gain a level. Done. That's what it's there for, so to speak.

For gaining warlock levels, there's no particular reason the dealing aspect can't be background stuff downtime. But if it must be done during an adventure, probably best the granted power just happens between adventures (assuming that's when players gain a level).