The Gnome King is the antagonist of Tree World. He is an evil king who kidnaps critters and locks them away in cages. He holds the keys to the cage around a key ring on his belt. If you beat him, he will drop Tree Food or Vita Gems and you can rescue the Critter he took!
The Gnome King is the only character in Tree World to vocalize, not counting Poppy, Pippy, and Pappy's dialogue boxes.