So, I was fiddling with modifiers and noticed that the two regeneration modifiers work in an unexpected way; having a large negative modifier causes the character to take damage or have their mana drained entirely. Based on the fact that it is presented as a % modifier in the UI I had assumed it would just change the rate the two respective stats would regenerate. So "-50% Health Regeneration" would reduce the character's base regeneration by half for example.

I'm wondering if this is the intended behavior. I did make sure to load the mod entirely by itself to ensure nothing else was causing the behavior either.