Karl Thekla is a mage and a "friend" of Anders. He became a tranquil recently and resides in the Kirkwall Chantry.
Dragon Age IIEdit
Anders and Hawke enters the Kirkwall Chantry at night to save Karl, only it was to late. Kark was already turned into a tranquil by the templars. This angered Anders, causing him to let Justice out to kill all of the templars there.
After the fight, Karl is back to his noraml self for a temporarily time. Karl tells Anders that he summoned the Fade itself in the Chantry in a way. Karl asks them to kill him, since he rather wants to be dead than a templar puppet. Anders tells Karl he's sorry and kills him out of mercy.
If Hawke goes to talk to Anders after gaining the maps, he will reveal to them that he and Karl were once lovers.