Immediately after this, Matt fell backward as exhaustion hit him hard. The strength he had unleashed to stand up to the devourer and kill it left his body then, and exhaustion hit him even harder as pain seized his body as a torrent of evil energy swirled throughout his body.
Even his ability to think had been slightly diminished. The fact that he had used his freezing curse while his body was straining at its maximum capacity to be able to keep that power in his body ended up giving him a painful punishment, as he found it difficult to breathe or even move.
Still, he had completed his task this time, which made him feel good. He had come to an unknown world with unknown and powerful beings, but this confrontation gave him the confidence to walk it the same way he once walked his original world.
If pain was necessary to gain that confidence, that was fine. He didn't mind feeling pain and fatigue, so he was perfectly fine.