Doren
We never actually get to see Doren, only hear of him. After the death of Erwin's parents, he took him in and raised him. He taught Erwin the art of swordsmanship. Due to Erwin being a descendant of light, he was in the way of Böser's plans and was to be removed. Böser sent Faias to do this. When Faias made an attempt on Erwin's life he stepped in to defend him. He gravely wounded Faias but lost his life in the process. It's because of this event that Erwin wanders, searching for Doren's killer.