From SA Mafia Wiki
A cult begins the game with a Cult Recruiter and sometimes additional cult members. Each night the recruiter targets a player to join the cult. Generally, recruiting cults do not also get a Nightkill. In most cases, cult recruiters can be Roleblocked so that the cult gains no new members.
Cult members are generally allowed to communicate with each other outside the thread, like Masons.
There are many variations on cults. Often, the recruiter will die if they target a non-Town player. In some cases, attempted recruits will be given a choice whether or not to join the cult. Power roles may or may not continue to be able to use their night action after being recruited.