De'Cine was an intergalactic criminal.
He seduced Sazu, the queen's handmaiden, and together they formed a plan to take over the throne. Maxima was lured away to Earth with the promise to make Superman her husband. In the meantime, De'Cine took over the throne from the highly spoiled and unpopular queen.
The first thing he did when Maxima returned with Superman was order them to the catacombs. Sazu, who had outlived her usefulness, was also sent below.
De'Cine quickly made himself comfortable, using his own bodyguard to protect him. They were needed when the three prisoners showed up in the throne room, with help of Almerac's own army. His guard was defeated by the queen, but De'Cine captured Sazu. She freed herself when De'Cine was knocked out by a guard.
Realizing his plan had failed, De'Cine made a run for it. Maxima threw an ax in front of him, causing De'Cine to trip over the handle. De'Cine was spared from death by Superman and Maxima ordered him to be locked up for the rest of his life instead.
Shortly after De'Cine was taken away, Lobo came to retrieve him for crimes committed on other planets. De'Cine's fate afterwards is uncertain.