ToME: the Tales of Maj'Eyal

I am currently unable to progress with my doombringer because, shortly after the boss in the anteroom or pain appears (it seems to happen after he reanimates some demons I've killed), the game freezes and then my computer stops sending any signal to my monitors. The only way to fix it is to forcibly reboot my computer. Any idea what could be causing this?

Probably a shader issue.

Sounds like a likely possibility, considering I was able to get past it by luring the boss's minions away to kill far from him and then killed him in a way that mostly kept him off the screen...