Ice Thing kinda made me think of Magwood when I immediately saw it.

Maybe those gems some how got into the lava and shaped the dog/elephant creature from it. So then it would explain how the will of the gems in combination with Dino-Gunter’s wish would shape the crown itself into a being emulating Evergreen.

Though that doesn’t address the obvious resemblance of Tree Trunks to Magwood. I think maybe Tree Trunks is possibly what’s left of the husk of Magwood and when she ate the Crystal apple in one of the early episodes of Adventure Time she temporarily regained the great power she once lost.

Not to mention their names MagWOOD and Tree Trunks.

The show kinda hints at the idea things aren’t what they may seem. These cute little (and not so little) innocent creatures: Gunter, Sweet Pea, maybe possibly Tree Trunks can carry the potential for great power and destruction within.