Capítulo 224: Chapter 224: Elemental Bomb

That wouldn't be fun... (Also there's another reason... Due to the bomb using it's own mana, unless you imbue it with an element, it won't affect the user. If he did use magic, it would expose himself to the school due to it being a mana spot as well. Mana spot will blend with mana spot so technically, he's using the school's mana instead of his own. This way, there's no difference between his usage of mana and the schools. No one will know he was using magic.)