Gene Simmons was one of the Great Beings who fought in the Uterio War.
During a meeting of the Great Beings' Council called by Angonce to discuss what should be done about Uterio di Armechio, Simmons sided with TPK's suggestion that the Great Beings should side with the Rebels to destroy Uterio once and for all. When Uterio charged in and broke up the meeting, Gene escaped to the ZFT homeworld with the other TPK supporters.
Later, when ZFT implemented "Plan 7", Gene, Bubbles and Armitage were chosen to lead the deliberately doomed assault on the GB fortress of Corrantia. He led a fighter squadron during the battle, but was shot down by Corrantian defenders. He crashed into a turret, and was killed instantly.