Humongous serves as a, well, "humongous" defense against city intruders and invaders alike. He is composed of two body halves, each half on one door of the inner gate to the Goblin City. When the doors close, the body fuses together and breaks free, attacking with a giant axe.
Humongous has a deep, reverberating voice and only seems to say "Who goes?" Interestingly, no one tries to answer, which might very well have stopped the attack, given the Labyrinth's penchant for obvious answers as solutions.
While attacking the human girl Sarah Williams and her friends at the city gates, Humongous is revealed to be a mech suit piloted by a tiny Goblin, even smaller than Hoggle, who reveals wings as he flutters down when defeated and the head of Humongous is ripped off.
It is unclear whether Humongous was the one speaking or whether it was the goblin with its voice mechanically altered, as the goblin has a larger vocabulary.
Appearances in other media
In the manga sequel Return to Labyrinth, Humongous is among the players in a sports game held to entertain Sarah's half-brother Toby, though curiously smaller.
Humongous will feature in Archaia comic's Labyrinth short story Hoggle and the Worm.