Gelgar was a young man who had brown hair that he styled in a pompadour. He had a prominent nose, and wore the traditional Survey Corps uniform.
He was very serious about his job, and believed strongly in Mike Zacharias' decisions and abilities. But when given the chance, he was also able to relax when he or his subordinates were not in danger. And like many of the Military personnel, he enjoyed drinking alcohol.
Gelgar had a defeatist mindset in the later part of the attack on Utgard Castle. As shown when he gives up and allows himself to fall into the Titans' grasp after his blades and gas are exhausted.
Gelgar is one of several soldiers brought by Mike Zacharias to oversee a group of potentially untrustworthy Survey Corps recruits. Before an investigation can begin, Titans appear within Wall Rose. Mike orders the group to split into four squads to warn the nearby villages and Gelgar is placed in charge of the South team.
Gelgar's team makes their way to Ragako village, Connie Springer's hometown. He and Lynne try to keep Connie's hopes up about potential survivors, pointing out that there are no signs of blood or bodies. However, despite his encouraging words, Gelgar secretly remains skeptical, taking note of the fact that the village's horses are still tied up in their stalls.
Later that night Gelgar's team investigates Wall Rose for a breach. Gelgar's team spots Nanaba's team and both are shocked to learn that the other could not find a breach. The teams consider searching again, before deciding to take refuge and rest in Utgard Castle. As the teams set up camp within Utgard, Gelgar finds a bottle of alcohol, though he cannot read the writing on the label. Gelgar tells the recruits to rest as the top soldiers keep watch.
Utgard Castle soon comes under attack from numerous Titans capable of moving during the night. Since the soldiers who had been under suspicion do not have vertical maneuvering equipment, Gelgar and Nanaba take the lead in engaging the Titans. However, Gelgar quickly runs out of swords and, after sustaining a head injury, loses the strength to continue fighting.
He falls off the Wall and is thrown into one of Utgard Castle's rooms by a Titan. Spotting the bottle of alcohol he found earlier, Gelgar is mortified to learn that the bottle is empty. Gelgar spends his final moments before being grabbed demanding to know who drank it.
As Erwin Smith contemplates his role as Commander of the Survey Corps and the lies he has told his comrades, he envisions himself standing atop a mountain of corpses of the soldiers he sent to their deaths. In his mind, Gelgar is with Nanaba and Mike at the top of the corpse mountain, staring back at him.
Gelgar's statistics as of year 850:
- Gelgar ranked thirty-forth in the Second Character Popularity Poll.
- Gelgar ranked twenty-eighth in the Third Character Popularity Poll.