Hey Leigh! I was wondering, do the corporalki have any effect on someone like the Darkling?

Absolutely. As I’ve mentioned before, the Darkling isn’t immortal. He can be hurt or killed. That said, if you were looking to do him harm, you’d have to get close enough to attack and make sure to hit him hard enough that he wouldn’t recover. You do NOT want a cranky, wounded Darkling coming after you.