The Mana Drain was previously just a weak Tier 1 Mana Art that can only be used when the target is not resisting at all.
Any form of resistance or even just a simple circulation of mana within the body and the Mana Drain will be disrupted and canceled. It is basically unsuited for battle.
However, after Vincent practiced the ability silently every day like how he grinds his other Tier 1 Mana Arts, it continuously improved.
From the beginner to the intermediate stage, he had already seen some improvements. Reaching an advanced state allowed him to strengthen the draining ability of the skill. Furthermore, draining was just one of its effects as it could transfer the mana into his body. It's more like a Mana Extraction for Vincent.
Of course, thanks to his Synthetic Celestial Core, the mana being transferred was easily converted into a minuscule amount of Pseudo-Celestial Energy… It may not be a huge amount after being filtered by his core but it's still better than nothing.
