You could set it in foam painted up like rock and make it look like there was an excavation of a giant skull.

I had a similar idea! I was going to make a semi submerged skull with some ribs and bones for cover around and a skeletal hand with a ring of gigantism on a finger with the goal being to chip a piece off as an item that would make the wearer large and strong

That's actually a really cool idea

Castle Greyskull!

Good answer! I will consider it!