I killed every Magister I saw because there's literally no reason not to. They imprisoned you, muted your source power and are constantly being massive dicks about it. What's even worse is that they all share telepathic knowledge.

Try killing the first Magister in the wake-up room. As soon as he's dead the three behind the door will rush inside which is totally fucking stupid. And not only that, all prisoners including Lohse, Red Prince and Ifan will immediately join the magister to look for you.