The Skull Night described it as an "unyielding fire that never goes out" and the hellhound seems to indicate the armor takes its power from some very dark emotions. It's not that it's cursed, it's just a dangerous magical item. And Ood is just their word for chakra, reiatsu, ki, etc.

Also, this isn't final fantasy bro, i don't think Guts will ever go from a Dark Knight to a Paladin.