After killing Don Dolnero he becomes the final antagonist of Mirai Sentai Timeranger.
Originally, Gien was actually an uneducated, human boy who befriended Don Dolnero in 2990 when he was hiding from the Kuronz Family, who nearly killed Gien for refusing to reveal Dolnero's location to them. Dolnero saved his life by having a friend of his transfer the boy's brain into a robotic body. However, though Dolnero's intentions were pure, he is horrified to find the side-effect from the surgery are making Gien increasingly insane with no care but for his own masochistic pleasures, going against Dolnero's orders sometimes as well.
Later in the series, beginning to act out his desires of mass destruction, Gien discovers the Hell's Gate Vault, where the worst prisoners are contained. He also also constructed several massive robots powered by the Lambda-2000 crystal he stole twice from Kawasaki Laboratories, and attempted to take control of the V-Rex as well. Dolnero, concerned and seeing his friend's antics bad for business, attempted to latch an attachment on Gien's brain to purge him of his personality and regress to his original mindset. But it eventually failed as Gien, seeing the G-Zord in action, created a device to drain the power from the G-Zord and Timerangers' robots. Though the G-Zord was destroyed, Gien used the Lambda-2000 he stole to assume his predestined role as the "God of Destruction", killing Dolnero when he attempted to stop him.
Finishing the Neo Crisis robot, Gien wired himself into his creation as he destroyed everything in his path. After Tatsuya saves the future by destroying Neo Crisis, Gien's previous memories resurface and he dissolves away into sand.