He hadn't involved himself in the conflict. It wasn't his fight, and Thanatos isn't a god of violence in any respect no matter how he might feel about one of the participants.

Afterwards, though, he finds Caster in the midst of the destruction she had wrought and picks his way between the still-cooling embers of the fire, the small flames still burning, the ash and blood and... he finds her. He finds her and stands over her for a moment, before letting out a soft sigh.

"Is that what you'd ask of me?" he says quietly, planting the base of his scythe lightly against the ground. "You should know that isn't part of my nature."