He swallowed Finn, Betty Grof and the Ice King, breaking them down to their original forms and nearly erasing them from existence by crushing them to death inside his body.This resulted in the treehouse of Finn the Human and Jake the Dog to be destroyed. His monsters defeated most of the Candy Kingdom army and prepared to destroy the rest of the world for their master.GOLB's monster then killed one of the Gumball Guardians and corrupted the other one into a similar creature.Many of the soldiers were shown to still be alive and in constant agony. The first thing he did upon being summoned to Earth after Uncle Gumbald's defeat was to transform at least hundreds of soldiers into a monster that would spread destruction for him.This is the main reason why Magic Man became a villain himself. He attacked Mars at some point, resulting in the death of Magic Man's wife, Margles.
He is also implied to have created, or at least influenced The Lich, making him responsible for many of the Lich's crimes. His essence was used in the Mushroom Bomb, which resulted in humanity nearly going extinct.
