Long ago, slayers were only used to keep the peace. They only killed a vampire when they killed a human. They were, essetntially, a police force. There would be times where they would even work with vampires to take on werewolves and demons. It was their way of keeping the towns safe.
Though, some people were not happy with this coexistance. Using dark magic, they began killing vampires, and humans who befriended them. Slayers were not safe from these Dark Slayers, and their numbers soon dwindled down to nothing. When these Dark Slayers were certain there were no more vampires, they vanished into the shadows, seemingly dissapearing forever.
It is now many centuries later, the year is 2013, and many things are still the same. The slayers still go after the murderous vampires, though now, they too are skilled with their own magic. The slayers though still know of the tales of the Dark Slayers, and keep a watch out for them, along with the heads of the slayer coven, and the Vampire Council.
The Dark Slayers are returning, and they want to finish what they started....