Thren is not into practicing blood magic at all. He doesn't trust himself with any real destructive power.
Thren really actively practices only healing. He tries not to tap into magic at all, and finds it a large struggle, especially in battle.
Thren would find Coan a little sheltered, but I think he's the relaxed apostate up for the magical introduction.
Thren is more about careful observation of the people around him, and I think that he would be happy to be around someone who doesn't really have much of an opinion about mages.