That would also lead to some interesting questions if you give it a divine aspect.

If it's all arcane magic, obviously sure, that all works.

But what if they need a cleric? That means there's a god out there who condones this sort of thing. And that god can do this with the souls of unbelievers... unless they prepare the condemned by making them believers, possibly through gruesome means.

Honestly it's more grimdark than I'd usually run a game, but it's entertaining to think about. :P