Fallstick provides his people with protection in the wilds, where they hide out, as well as tending to their wounds. In exchange, they willingly provide him with their blood, which enhances his powers.
The cult adheres to the Old Gods, a religion which was widely popular in ancient times, but abandoned after the First Blight. They do not see blood magic as evil, but as an alternative, more powerful source of power. They despise templars for hunting down and murdering maleficarum for simply practicing this ancient form of magic. They share this belief with The Man of Light.