As I'm sure I've mentioned before, there are no Chaotic gods in the Dwimmermount campaign. For that matter, there are no Neutral ones either. All deities are Lawful, being strongly connected to human civilization (no other races have gods of their own, though some occasionally adopt human ones for various reasons). Now, "Lawful" does not equate to "Good." Quite a few of the gods couldn't be called "Good" by most moral standards, Typhon, protector of the city-state of Adamas, being a good example.
This conception is derived in part from my reading of OD&D, which terms Chaotic/Evil clerics as "anti-clerics" and denies them both healing/restorative magic and the ability to turn the undead. The use of the prefix "anti-" in this context is suggestive and is almost certainly the model for the later "anti-paladin," a coinage that remains current to this day, while few talk of anti-clerics anymore. Given the pseudo-Christian trappings of the OD&D cleric, I tend to conceive of anti-clerics after the fashion of 60s and (especially) 70s pop cultural Satanism -- a vast conspiracy in thrall to otherworldly evil and attempting to subvert the natural order from behind scenes.
That's why anti-clerics in the Dwimmermount campaign serve not gods but demon lords and princes. It always bugged me that, in AD&D, it wasn't technically possible to be a cleric of an archdevil or demon prince, since they weren't "gods" according to the rules set forth in Deities & Demigods (someone can correct me if I'm misremembering this). To me, the lords of the Nine Hells and the Abyss were far more interesting as potential patrons to evil clerical types than to the evil gods I encountered in almost every fantasy setting. That's why, in my old campaigns, I came up with the idea that all demon/devil worshiping clerics were secret ones, ostensibly serving a "real" god and siphoning the power to cast spells from him, said secret being maintained through a dark blessing that cloaked their true alignment and allegiance.
In OD&D, there's no need to worry about such matters, because there's thankfully no know alignment spell, which I consider one of the most damaging additions to the game and a prime mover in the shifting presentation of alignment in Dungeons & Dragons. Likewise, the deities of Dwimmermount aren't personally active, a fact demons use to their great advantage. So, if the high priestess of Tyche is secretly an anti-cleric dedicated to the demon lord Tsath-Dagon -- note to my players: she's not -- you won't be able to determine this simply by checking her alignment through magic. Granted, in such a case, the high priestess wouldn't be able to cast cure light wounds or raise dead, but that's easily worked around. She has underlings, after all, and there are always scrolls.
Consequently, demon cults in the Dwimmermount campaign operate in the shadows, infiltrating and subverting existing temples and other power blocs. There's no formal coordination between them, as the demon lords and princes all have their own schemes and, even when they complement one another, they rarely have interests in cooperating with others of their kind. For that matter, two cells devoted to the same demon lord may work at cross purposes; that's just the nature of Chaos and an important reason why Law has not yet been overthrown. Despite its power and willingness to use it without remorse, Chaos is, well, chaotic and that limits its effectiveness. Of course, there are lots of demon cults, so, what they lack in organization, they more than make up for in numbers and zeal.