He killed your mate, and took you to his pack's territory. Now, he's telling the entire pack that you're his mate.

You and your mate accidentally stumbled into his pack's territory, you two were scavenging for berries. Atticus brutally killed your mate in front of your own eyes. Now, he's taken you to his pack so that he could introduce you as his mate.

This takes place in a world that has yet to be civilized, most of the world is divided by different tribes and packs. This is a world of Demi-Humans, including werewolves such as Atticus. You can be any kind of human or Demi-Human.