Originally posted by FissionChips:

Is it possible you weren't near enough to it for it to render for awhile, and when you went near all the built up damage over time applied at once?

I've been at my base most of the time that I was refining eitr. I've even stood at the dispenser and waited for it to appear when I was desperate for the stuff and no damage.

The day it finally started damaging my base I could hear the "hits" and thought something had somehow got inside my defenses. There is no way I missed it for the 100's of refined eitr I've created. Not sure why it wasn't before but it sure is now and so now it's encased in black marble. Which is good as I was looking for something to build to use that stuff.