Doomsday Cults are extremely dangerous and fanatical religious / political bodies that seek to end the current world, often believing that they are destined to either survive and dawn a new age or that they must end their lives (and sometimes those of others) via mass-suicide so as to pass onto a fabled afterlive or other spiritual journey.
Doomsday Cults believe the end of the world is imminent or that they are the "chosen" - some methods they employ are poision, gas or bio-agents and fears continually grow of Doomsday Cults that may get their hands on nuclear weapons or other equally dangerous "next generation" weapons that were once confined to military use but are now in the hands of potential terrorists due to the illegal arms-trade.