The counterweight is the skull of an ancient mother grub, slain thousands of solar sweeps ago.
The egg contains a rare species of dragon which remains blind until maturity, using its other senses to survive. It has balanced the skull here for millennia, waiting for the warmth of a meteor-sparked forest fire before hatching.
Hey check it out. Every week we'll be revealing some new troll characters from Hiveswap until Act 2 is out. Follow the Troll Call here, and meet the first two here. Expect a few more surprises like this to drop in coming weeks.