In primitive times the Shadow Men, three sorcerers, took a young human girl and imbued her with the heart of a demon, giving her the inhuman strength needed to hunt and fight vampires. Since that time, girls have been born with the potential to become slayer's, recognizable only by the birthmark on their shoulders. There can only be one active slayer at a time, and when she inevitably dies, another one is called to take her place. The Watcher's Council was formed to seek out potential slayers at an early age and train them so they are ready should they be called.

Having to keep her identity secret, a Slayer's life is a lonely one, often parted from her parents at an early age, the only person she will know is her Watcher. If called, her tenure as active Slayer is often hard, brutal and short. At least this was the case until Buffy Summers was called in 1996

An 'it' girl at LA school, Hemery High, Buffy had her birthmark removed and so became difficult for the Watcher's Council to trace. When they finally did, she was unprepared and her first Watcher was killed and she expelled from her school. Moving to Sunnydale she found another Watcher waiting for her and slowly came to accept her duties and juggle them with school and a social life. Having a close circle of friends around her gave her strength, and when she died, they were there to bring her back - twice.

When the First Evil comes to town to open the Hellmouth and destroy the world as we know it, Buffy finds a scythe and, with the help of her best friend and powerful witch, Willow, uses it to give slayer stregth to potential slayers the world over. Changing slayer history forever.

At least in part due to this action, vampires and demons are eventually expelled from our dimension and the need for slayers is erased, until the threat returns and another is called: Fray