Who is Teferi from My Soul to Keep and what is their importance?

Teferi is one of the Life Brothers who goes mad because he spends too much time with mortals. It is because of Teferi that the Seekers are created to search for and monitor Life Brothers who have spent too much time in the moral world. In Turkey, Teferi had killed a dozen people in a market place. When Mahmoud first visits Dawit, he tells Dawit that his actions remind him of the way that Teferi acted just before he went mad.