Minor spoilers for Rock Falls, Everyone Dies (read it!):
The flashing thing screeched in rage as the golem fell, dissolving into muck and rocks onto the ground.
We never did find out more about that bone core. I wonder what its deal was? Where did it come from? Where was it going? What was it doing down there?
(I'm glad I documented the spoiler text solution I used last time, because I'm using it again.)