Also, [@Rtron], I should point out that when you corrupt the Holy Wisps, you cut off their connection to the Orb of Escry, this removing them from the hive mind. Without something to link together your Chaos Wisps (that's what I'm gonna call them) like how the Orb of Escry does, they're going to aimlessly wander around the world by themselves and die pretty easily if they get attacked. Imagine an ant separated from its colony. That's basically what they are now, unless the corruption has somehow increased their intelligence or something. You could also make a new host mind, or use Vestec's mind to do it, but I'd imagine that the latter would be annoying even for a god to manage.

Of course, Niciel could always just go out and purify the Chaos Wisps back into Holy Wisps, thereby making this entire explanation completely unnecessary.