Magmass is a 300-foot lava Dragon who appears as the seventh boss of Goop's World, appearing in the level Magmass's Core. This level is the last level in the Mount Fireside. He is an enormous serpentine dragon with stone spikes down his back and a flaming Fu Manchu. His entire body is wreathed in flames and he possesses the ability to breathe fire, spit lava rocks from his mouth, and fly without any visible wings.
Magmass later reappears as a massive skeleton shortly before the final battle with Grex. Sometime between games, King Grex killed Magmass and put him on display as a massive skeleton for eating him. At the end of the game, King Grex is once again eaten by the undead Magmass, resurrected by Bing off-screen.