For y'all who are confused about Thomas he's not a demon. He's just insane. It's a mental disease that he's trying to fight but he basically has two sides. Both are extremely broken.
One is his "sane" side, the side he normally is.
The other is his "insane" side, the side that he will basically turn into the joker. Giggley and murderous.
Thomas will bounce back and fourth and try to stop himself from doing certain things but it hurts him.