Well, there’s The Wolf Cult. Frequent RP in Duskwood, rituals and initiations, spreading the worgen curse, etc. Not much in the way of undead or elves, but a Deathknight worgen has joined us recently, and playing a Kaldorei-Worgen is possible as well.
[A-RP] <The Wolf Cult> - Wyrmrest Accord - World of Warcraft Forums
I’m trying to think of other cult guilds around. I know there are… or at least were a few, but I’ve found a lot of small guilds don’t post on the forums. Roleplaying in Duskwood so frequently, I’ve also seen a guild that frequents Darkshire (Malum Discordiae) but I know next to nothing about them.