@Raowaa
Final Edit: added some extra lines and fixed a few mistakes I found after going back and re-reading real quick.
His cursed eye reduces his opponents maximum HP by reducing his own maximum MP.
This makes him really scary in a 1 vs 1 combat.
Also because he for some reason gets more int and wisdom per level He is eventually going to get enough mana to drop somebody's HP down to 1 or even 0.
I'm assuming its an automatic stat distribution ( or no stats per level at all ) because the evil merc had 17 ints and was unable to use magic as far as I can recall.
( we never really seen a mage character yet however so take this with a grain of salt as it's only my prediction )
Actually, the evil merc seems to have had "magic mastery", so it's possible he was able to use magic but just didn't because of how unstable he was.
That changes a few things...
And while not yet confirmed, it also seems to trigger a fear response in whoever he uses it on (
or he is just REALLY scary looking with black eyes )
@SeryjVolk
There is however unlikely to be a time variable in his skill, as he nerfed somebody's HP by 239 in what appeared to be a few seconds.
Unless you count the time he was looking at him before he used the skill too, or that it's a slow drain that happened off-screen as you said. ( not that strange for a curse I guess )
The reason it stopped at 239 was that the MC ran out of maximum mana after dropping to 1 / 1
( we are actually unsure if the evil eyes actually cost mana or only reduces his maximum, if not he could use spells to buff his party or CC before nerfing somebody to high heaven )