I immagen after losing Hauchefaunt, Ysale, almost losing Y'shtola, and the fact that most of the scions are still MIA probably had good old Magnus at the boiling point.
Add that to all the dark, savage, and arcane powers he's mastered along side the eye of the Dragoon, not to mention Blessing of Light 2.0, and I'm sure the pure hate Magnus was feeling for Tborden, the Knights, and the Ascians gave him quite a "God of Death" vibe when Tborden saw the inner Darkness I was hiding.