Werewolves
Long time ago werewolves and humans lived peaceful together. Werewolves were the dominant species at that time, much hybrid came along as the werewolves took back a little and let humans live in peace. A war was announced when the humans started fighting with a nearby pack. After decades of fighting and damage, the werewolves and humans came to an agreement that no more harm would come to either species.
Now, 150 years later, the peace treaty between the humans and werewolves was becoming strained. The new generation of werewolves needed fresh blood and the humans were the closest and best choice. The pack leaders met to discuss what needed to be done. The new wolves would group together, picking out their mates and they would descend upon the humans. Whether or not it was going to be a peaceful meeting or one of danger, would depend on how well the humans would adapt to being with werewolves.