For some reason, there is a recent (last decade) trend of magic-users being attacked by, tempted by, used by, or in some other way being manipulated by demons. Two examples off of the top of my head. First, in EVERY Avernum computer game in which it appears, the Tower of Magi (later known as the Tower colony) is attacked by demons, or else has demons from a previous attack still hanging around it. The second, and much-better publicized is Dragon Age: Origins, in which EVERY mage is tempted by demons, and they even have to pass a test to prove that they can resist demonic possession, or else they are killed or lobotomized to prevent possible infestation.