Geatar was second in command of Nebula's crew aboard the spaceship Sanctuary III.
Upon Thanos' return from death, Nebula did not believe this to be the true Thanos. Geatar attacked him and was destroyed. Thanos then altered Geatar's body to resemble his own in order to fake his own death. Surfer returned the body he believed to be Thanos' to Titan.
Mentor was able to reconstruct Geatar from the DNA matrix in his cell structure and revive him from death. He vowed to continue serving Nebula, who was in the custody of the Titans after the Infinity Gauntlet.
He eventually gained the trust of the Titans. One day while serving Nebula some food he grabbed her to help her escape. He killed a guard and took Nebula to someone who could help, a criminal doctor named Doctor Mandibus. He offered Geatar a chance to change Nebula into whatever he wanted, but he just wanted his captain back with the same personality as before. Nebula was repaired and told Geatar that she would repay him some day.
They first attempted to retrieve the rest of their crew who were on the prison planet Annoval 14 in a supermax prison known as the Anvil. Geatar took in Nebula and offered her as a prisoner. The Chancellor knew all about their situation and knew Geatar was in on it. But Geatar turned on his captain and turned over his weapon and met with the Chancellor. He claimed to want a job and as soon as the Chancellor turned his back, he took the Chancellor's electric rod and attacked him. He took him hostage and went to free Nebula.
On the way to free the crew they ran into the Silver Surfer. They threatened to kill the Chancellor, so the Surfer did not interfere with their plans. But when they got their crew to the largest ship available, the Jack of Hearts was waiting for them. Jack of Hearts and the Surfer proved more than the entire crew could handle and Geatar was injured. He told his captain to leave without him but she told him she would repay him for what he did for her. They got on the ship together and started it up, killing the remainder of the crew with the ship's jets. Nebula said that there are few things she holds dearly, but her first officer was one of them.