Once a slave of Danarius, a Tevinter Magister, Fenris bears markings of lyrium on his skin that have granted him the unnatural ability to phase through solid objects. Fenris uses this ability as a weapon, phasing through individuals and solidifying, killing them violently. However, the experiments performed on him also caused him to lose all of his memories. He has fled to Kirkwall as a fugitive, hunted by the soldiers of his former master. The lyrium burned into his body causes him pain, making him guarded against physical contact; however, it is more of an aversion to them being touched rather than physical pain.
Being a former slave himself, Fenris is happy to help slaves flee their masters or kill the ones who hold onto their chains. Because of his unpleasant experience with the Tevinter Magisters, he is extremely distrustful of mages. He feels that they would do anything for power and inevitably succumb to the temptations that demons and blood magic have to offer.