Toz had lowered the defenses on his mind. He had thus managed to regain some control of his breakthrough and his body and the mana ravaging it. But that did nothing to alleviate the sensation of having his body filled past the point of exploding with mana. There was also the fact that his body was on fire. And after that came the feeling of having his mana pool expanded to the verge of shattering.
The more Toz lowered his mental defenses, the greater clarity he had when it came to the outside world and the state of his body, which allowed him to contribute more easily to his breakthrough. But it also meant that he felt his pain that much more clearly.
The pain of his body repeatedly burning and recovering was especially excruciating. And if it weren't for the breakthrough and the mana storm locking his body in place, Toz was sure he would have screamed himself hoarse. But he couldn't even open his mouth, much less scream, despite the pain assailing his body.