The Darkness can be hired by those few that know, for a nice sum of course. If they accept a target (how do they choose their victims is unknown), after a short time the victim mysteriously vanishes. Some in need of assasination prefer this, for if there is no body, there is no evidence, and instead of becoming a heir and prime suspect, one can silently steal that wealth, have the woman they love, etc.
Strangely enough, nobody is killed. The sect believes in the coming of an Ueber-human (or dwarf or elf or what), that is subconsciouly battled by the average people, that shall be replaced eventually. So if somebody is to be killed, it may be the ancestor of the True Man! The victim is actually kidnapped by the sect. (The diffilcuty of doing this decides if they do the "kill", and what price they ask for. Consequently, people of real power, with good bodyguards are rarely accepted as targets.)
Despite the saving, these are no friendly guys. The victim is completely brainwashed, and sent into some other cell of the sect, as far as possible. Living in the darkness they must tolerate until the Coming, helped with drugs along, the victim forgets most of the former life, and lives fanatically for the cause.