Complex sentence: Since the first episode of season 2, Graubaer's Boker has appeared in an uncredited role as Bear, a Belgian Malinois with military training who Reese rescues from Aryan Nationalists, who were using him as an attack dog.
Split into simpler sentences: Since the first episode of season 2, Graubaer's Boker has appeared in an uncredited role as Bear. Bear is a Belgian Malinois with military training who Reese rescues from Aryan Nationalists, who were using him as an attack dog.