Do I need to force him to use up all his Mana before I can defeat him, like with the Demon Lord? Or does he have some other weakness? I wiped out most of his body with that last attack, but he regenerated in no time.
And while it does look like that consumed a fair bit of Mana, his regeneration is a lot more efficient than the Demon Lord's was, though it's also slower. So, while he can't regenerate quite as quickly as the Demon Lord could, he won't burn through as much Mana doing so.
But more importantly...
"Is there a reason why you're still holding back? That Divine Art called Ascent, why haven't you used it yet? It's a power boosting ability, isn't it? Is there some downside to using it?" I inquired, narrowing my eyes at him.
"Oh, I'm under no obligation to answer your questions, mortal," He replied with a shrug, as he formed a ray of light over his crotch, my previous attack having eradicated his trousers.
