Definite Proof

But Ace knew that the point was not that. In the first place, Cloud's skill was continuous. So, after she used it, it was almost guaranteed that the skeleton who only had ⅓ amount of his original HP when it was still alive was sealed to die in less than 10 seconds.

And she could target another skeleton after 3 seconds of cooldown of the skill ended. So even before the first skeleton that she had targeted died, two other skeletons could be targeted. And the fact that the skill's mana consumption was so little, made this skill broken. The skill that Ace thought mediocre in the past had transformed into such a terrifying skill for the undead. 

And Ace just remembered that Cloud had a necklace that she bought in the system shop in the past. This necklace doubled the mana amount of Cloud. He almost felt pity for the undead.