Awesome work! I really like the Necromancer's Den. That was my favorite, however, there were a lot of auditory pops and clicks within the sound. Not sure if that was intentional or not, but it was there! The ambiance, though, felt spot on and similar to the feel I was also going for with this challenge (dark and gritty).
The spellcast SFX was a bit too long for what I would typically think a cast would be (in terms of the tail). And the wall crumbling had a much lower fidelity (i.e. quality) compared to the other two and there was A LOT of reverb. I guess it depends on the setting cause it could definitely work in a cave setting! Awesome stuff overall :)