1. I heard a song on my way home tonight that inspired a small, quick thought:
The song is December by Collective Soul. The opening line is "why drink the water from my hand, contagious as you think I am?"
I imagine cancer mages and other disciples of disease forming one of the myriad cults in Wyndhaven would initiate novice members by the ritual of drinking water (or some other liquid) from their hands. These novices would not necessarily know that they are being inoculated with a disease that would test their fortitude and favor with the dark gods of disease. To survive the course of the affliction would prove they were worthy to be indoctrinated further into the fold. Any disfigurements would be badges of honor. Those who died still served the cult's purpose, especially if they infected others before passing.
2. The second cult idea is stolen from Fall From Heaven. Since it is stolen so wholesale from the game, I will simply reprint the Civilopedia entry for the Zealot unit:
I have not been able to discern how the Cultists choose their zealots. Sometimes it is a vagrant, sometimes the son or daughter of a noble, and everyone in between seems eligible. He is abducted and taken to temple, usually on the night of the full moon. The hands and feet are bound. Sleep is induced. Some sects use various herbal concoctions; this one simply strangled the man until he passed out. He is laid in a shallow pool, submerged partially in sea water.
All night the Cultists gather around, listening for anything he might say in this sleep. This becomes the zealots new name. It is etched onto a clay jar, which is filled with sea water. I observed the names on some of these. "The Leviathan Trembles But Does Not Awaken," read one. "Pour the Blood of the Slaves Into the Styx," another. The victim tonight seemed to hear nothing, for he was silent as he slept, nearly until dawn. Should this be the case, the victim is drowned and serves in the undead army of the Overlords. Fortunately for this man, or perhaps not, he at last called out screaming, "The distant one has watching eyes!"
The Cultists nodded to each other and pulled the man from the water. When he saw them holding him, he cringed. They spoke not to him, but dragged him to the back of the temple. I was unable to follow, but observed the Zealot days later in sea colored robes. He had bloodshot eyes, and moved through the crowd in the town marketplace engaged in a constant dialogue with himself.
From chapter 7 of Reflections on the State Cults, by Elder Methyl of the Luonnatar.
3. I am also stealing the Mouse King from Kobold Quarterly #4, but that is more of a thieves' guild than a cult. Just thought I would mention it.
4. And because I am already making this post, other Wyndhaven cults obviously include the Sons of Wrath (followers of Rath and mechanically similar to Ravagers) and the Faces of Fear (followers of Saren Kollmer).