I'll think about the charge thing. I'm trying to keep the systems simple and he already has so much damage but who knows lol.
About poison, yeah, I like that. Except I'll probably have to give the player a weaker variant since taking 10% of a boss' health would be overkill xD
Mao can't make his own poison tho, and I don't think I can make an item like the fire rag that gives normal attacks a chance to poison enemies unfortunately. But maybe a consumable item like the kobolds' grenade could work. I'm going to add a side quest soon which allows you to buy fire bombs, so maybe doing the same for the poison ones could be cool!