Honestly, the only notes I have would be to add spell variety and be a little more clear on the victims' status. It seemed like a lot of the ones I threw in the pit were already dead (or orange, though I'm not sure what that means), but they still counted toward the goal. And the stats screen showed a lower number of sacrifices than required, so I was just a little lost.
As far as spells go, I'd like to suggest a grab spell so you can quickly dispose of stragglers or near-misses without walking all the way around the pit to blow them back. Or just a dash to make that process quicker.
If you want to see my gameplay, you're first in the video!