Gim Allon, Leviathan, was the first official leader of the team, but resigned after one mission, following the death of the first Kid Quantum and realising that Cosmic Boy was more suited to the role - although Rokk persuaded him to take on the deputy leadership.
He then became ensconced in a love triangle, as while he nursed a crush on Kinetix, Shrinking Violet nursed a crush on him. This ended in tragedy, howeve, when the Emerald Eye - on orders from Violet to give each member of the team their heart's desire - caused him to die in battle with Doctor Regulus, fulfilling his wish to have a heroic death.
Powers and abilities
Leviathan could increase his size to many times the height of a human, with proportionate increases in strength and mass, and return to his original size.