I like building bases around the Bonemass skull. It's one of the few points of light in a swamp!

This is one that I just built for fun. I didn't fight Bonemass here.

https://steamcommunity.com/sharedfiles/filedetails/?id=2859785610

I have fought Bonemass a couple of times after building a (smaller) base around the skull, and the one time he spawned in the atic, half sticking out the roof, and appeared to be stuck, so I beat him to death!

The other time he spawned outside, so it was a normal battle, with just some minor damage to the building.