@Ladyalexia regeneration magic perhaps ? torture them for millenia by keep healing their wound and life force and inflicting pain to their body. And the glass might also some magic item that could capture soul
and by the looks of it, he could be throwing poisonous bugs inside there, like a BUG JAR
@mikoreimu I would guess that it could have something to do with chimeras, otherwise it would've been a kind of throw away subject to try to show the "dark side" of the current hero. If he made them into some kind of huge insect type chimera thing, and used his magic to stop them from losing their sanity and escaping the intense pain, then chimeras would've at least been kind of important enough to mention. Though he could of also made some kind of time capsule thing where they are all killed by giant insect monsters and then it resets over and over and over forever. Just some other ideas of what it could be based on what it's shown so far.
I guess that when you combine the powers of darkness and evil with being twisted by pain, grief and hatred for at least 7 generations, you would also end up a little less sane in the head.