Lets alter the compromise a bit: in official D&D, some yugoloths have become demons, throwing in their lot with the CE fiends for (insert potential reason here). In your games, or other games that want the 4e lore, some is all.
On the one hand I don't want to get too pedantic over a fairly low-stakes debate. On the other hand, it's still the case that this altered compromise requires me to retcon my game, in which currently there is no such thing as yugoloths having become demons.
For clarity's sake, I'm not saying that that's a reason not to adopt that lore in D&Dnext. My point is that all lore requires someone, somewhere, to either change their game or ignore the lore.
Though it's worth noting that this distinction may be largely academic in 5e. If all evil extra-planar critters are "fiends," what falls into Demon and what falls into Devil and what falls into Other is likely open to reinterpretation.
For my money that would be a better way to go, though it may fit unhappily with alignment rules.
Before the Blood War, there was no reason that a Vrock and an Eriyes couldn't work together.
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There's certainly nothing in the Monster Manual or Monster Manual 2 which would preclude a Balor and a Pit Fiend from having a drink together.
There was. It was called "alignment."
LE and CE don't get along.
Orcs, which in AD&D are lawful evil, are well-known for working with ogres and trolls (both CE). I'm less certain of my memory on this next one, but I think goblins (LE) sometimes work with bugbears (CE). When Last Alliances need to be formed, elves (CG) will work with dwarves (LG). And I think I can look at classic module rosters, as well as tradition, to see CG rangers working with LG paladins (who have a bar on associating with evil, but not with chaotic, individuals).
As an AD&D GM I designed and ran scenarios in which LE devils worked with CE demons, with no sense that I was breaking or even stretching the game's alignment rules.
But, in AD&D, Law and Chaos had no actual effect outside of alignment. It wasn't until 3e that you had Law and Chaos as actual effects in the game. There was no Hammer of Chaos spell in AD&D. Everything was based on the good/evil axis.
Exactly. AD&D makes it pretty clear that the L/C divide is less fundamental than the G/E divide. (As [MENTION=27160]Balesir[/MENTION] et al have pointed out OD&D and B/X are different, but in those systems devils would have to be chaotic - or, to put it another way, those systems have no real room for devils as distinct from demons.)
Yugoloths/Daemons have never just been a variant demon, until 4th Ed's lazy hand-wave.
Never, since their inception.
In Vault of the Drow, mezzodaemons and nycadaemons hang out with the drow, who are known to be demon worshippers. Like demons, they are extraplanar and tough, with some odd and somewhat arbitrary resistances, and a wacky new version of magic resistance.
In actual play, they play very much like demons. My view is that someone who had played Vault of the Drow, or who had used the Fiend Folio daemons, or the entry in the original DMG, and who then picked up 4e and saw that daemons had been rolled into demons, would not get any great shock.
I will assert the same thing for MM2 hordelings, also. I mean, what's the real difference between the system for random generation of hordelings in MM2 and random generation of creatures from the lower planes in Appendix F? At least at that time, AD&D simply didn't draw any major distinction between the play of these different creatures.
If I personally was carving up the MM2 daemons, I would make the dergodaemons (sp?), yagnodaemons and hydradaemons into demons, the arcanadaemons into devils (perhaps serving Amon, given they have similar jackal heads), charonadaemons and Charon into devils (who ply the Styx and make pacts with travellers upon it), and ultradaemons I might link up with slaads somehow.
Same with that botched alignment system, I mean, what was with the arbitrary truncation, they might as well have scrapped it completely (along with classes).
Given how heavily class-based 4e is as a game, I don't really follow the paranthetical comment.
On the alignment system - it's not arbitrary just because you don't like it. I don't particularly care for Planescape, but that doesn't mean it's
arbitrary. I assume that its authors had
reasons for what they did - they're just not reasons that speak to me.
4e replaces grid alignment, which I personally find hopeless both from the abstract perspective of moral and social philosophy and from the practical perspective of running a game, with spectrum alignment on the same plan as OD&D and B/X - only as well as of L-N-C we get "Good" to signal the friendlier, more Robin Hood-ish side of unaligned and we get "Evil" to signal the more ugly, selfish side of unaligned. Chaotic Evil is reserved for "Emirikol the Chaotic" types, plus their extraplanar analogues.
Like classic alignment, the whole system is predicated on a cosmological struggle built into the foundations of the game (which means, in my view, that it probably doesn't make much sense in a Dark Sun campaign except as a personality shorthand for NPCs). It doesn't pretend to be a catch-all system of moral/ethical classication.