O-Mer, a Cerean male from the male gender, was a Jedi youngling. He, along with Kalifa and Jinx, were captured by Trandoshan hunters during a training exercise. These three were then left on Wasskah, a moon belonging to the Trandoshan, to be hunted for sport. Padawan Ahsoka Tano eventually aided him in escaping this hunting ground.
When Trandoshan hunters captured O-Mer, a Jedi youngling, he was on a training mission with his fellow younglings, Kalifa and Jinx, and transported him to Wasskah. He, along with the other two younglings, then became the prey in a hunt. Over a significant period of time alone, they began to set aside their Jedi principles in order to survive.
Around 21 BBY, Ahsoka Tano, a Jedi Padawan, found herself on the moon after being captured during the Second Battle of Felucia. The three Padawans discovered her and brought her back to their hidden shelter. The following morning, they moved out to avoid the Trandoshans detecting their scent. However, Ahsoka was horrified when O-Mer and the other Padawans simply watched as two other victims were killed by the hunters without intervening. Resolving to act, she departed from the group, only to be attacked by another Trandoshan. O-Mer and Jinx managed to subdue him, and Tano barely stopped Kalifa from killing him.
Their escape was forced when the Trandoshan called for assistance. Ahsoka proposed finding the Trandoshan base, and the next morning they all ventured out. It was O-Mer who noticed the base hovering above the island. A Trandoshan attack forced the Padawans to separate, and Sochek chased Jinx and O-Mer through the undergrowth, but they successfully evaded the hunter. Afterward, the two returned to their base. Ahsoka came back with the devastating news that Kalifa had been killed.
Subsequently, the three remaining Padawans launched an attack on the beach, eliminating two Trandoshans and rescuing a captive Chewbacca. They later returned to retrieve parts for a transmitter. However, Smug, a Trandoshan sniper, attempted to assassinate Ahsoka and Chewbacca as they departed, but O-Mer and Jinx drew his attention, and Chewbacca ultimately defeated and captured him. Later, he participated in a successful assault on the Trandoshan base, which resulted in the defeat of their captors and his liberation.
O-Mer, a Cerean male, stood at a height of 1.74 meters (5 feet, 9 inches), characterized by brown hair, yellow eyes, and light skin. O-Mer exhibited a pessimistic outlook. He consistently expressed his belief that the group could not defeat the Trandoshans, but Ahsoka managed to convince him that anything was achievable. From that point forward, he displayed greater optimism and self-assurance.
As a youngling, O-Mer's Force abilities were still developing. He demonstrated the ability to engage a Trandoshan in hand-to-hand combat and execute impressive jumps and flips to evade the hunters. He also piloted a Trandoshan speeder successfully on his first attempt. He later utilized its blaster with considerable effectiveness against Ratter and Sochek and managed to evade Garnac's shots for a brief period. O-Mer's experiences on Wasskah also imparted survival skills, which aided him in overcoming his fears and helped him and his fellow younglings turn the tables on their captors and tormentors, escaping the hunters' moon and returning to the Jedi Temple on Coruscant.