Aliens and Deadly Cults

Mass suicides. Human sacrifices. Unholy rituals. Throughout history, people have claimed to have otherworldly knowledge, and have led followers to commit horrific acts of violence. Are they con men? Are they insane? Or might the voices in their heads really be of an extraterrestrial origin? And if so, did they simply misinterpret the messages they received? Or might there be extraterrestrials with a sinister agenda?