Quote Originally Posted by ebarde View Post
How hard would it be for a divine caster to just sorta adopt a new deity to mantain their powers?
The official rules (for 3.5, found in the FRCS and PHB II) say you have to accept a geas/quest spell from a higher-level cleric of the new deity and then complete that quest without access to spells or other divine based class features (domain powers, turning undead, etc.).

Under normal circumstances, in which a cleric is switching from one currently extant deity to another also extant deity, it obviously makes sense to impose a rather challenging quest in order to make sure that the loyalty is real, but in the case in which the old deity is dead and the cleric of the new god is aware of this fact, there's no reason the quest can't be something really easy, like "conduct the daily prayers to deity X for Y days, where Y equals your level."

The implication here would be that immediately following the death of Lolth (or really any other deity), a bunch of high-level clerics would descend on any concentration of the clerics of the deceased deity at warp speed making 'who wants a quest?' offers to anyone even remotely talented. This is particularly true of flexible deities of neutral or chaotic alignment, who probably don't care so much that this new branch of their faith is going to have some holdover quirks for a few generations. "Yes, yes, Shar is fine with you keeping the spiders, just make sure you only feed them at night now. We cool? Good. Everyone raise your black disks and repeat after me..."