Little is known about Gresh's early life. It is known that he was born on Spherus Magna later than all other Glatorian, given that he is the youngest. He has no memories of the Core War, but it is unknown whether he was born after The Shattering or just too young to participate at the time.
Years after the Shattering, the Jungle Tribe hired him as the second Glatorian of Tesara following the death of their original second Glatorian, making him the youngest second Glatorian ever.
He once had a match with Malum and lost. Later, when Malum tried to kill Strakk in the arena, Gresh jumped on him. He threatened Gresh, and Ackar said he would fight him if he did anything to Gresh.
Around 100,000 years after The Shattering, Gresh, Tarix, and Strakk traveled to Vulcanus, where Gresh battled a Skrall. The travelers came across a Bone Hunter named Fero attacking an Agori of Tajun named Berix. Launching a Thornax at Fero's hand, he saved Berix, only for Fero to flee and trample Gresh and his friends. After recovering from their injuries, they were almost immediately attacked by Malum's pack of Vorox, though Malum quickly called them off. Berix left and the three Glatorian left for Vulcanus.
He soon went into battle against a Skrall in the Vulcanus arena for control over an oasis. He faired well, lasting three minutes, which was the longest time anyone had ever lasted against a Skrall, before the Skrall gained the upper hand and defeated Gresh. The Skrall moved in to kill Gresh, but Tarix got in the way and saved his comrade.
Before an upcoming tournament in Atero, Gresh was practicing his battle moves in the wilderness with Tarduk, away from the other Glatorian. While he was practicing, he was confronted by Malum and a group of Vorox. Malum suggested that Gresh flee, but Gresh insisted that he would not run. Gresh was at the arena when the Skrall attacked Atero. He was ready to stand his ground and defend Atero, even if it meant dying. But in the end, he and the other Glatorian were outnumbered and forced to flee from the destruction in Atero. He and some other Glatorian and Agori later met in a cavern to discuss what to do.
Gresh later traveled to Tajun, to have a practice match with Tarix. Gresh was then attacked by a Bone Hunter horde. He was able to defend the village, but was defeated by a second wave of Skrall warriors. After the warriors departed, Gresh emerged from his hiding place, and told Ackar, Kiina, and Mata Nui about Skrall allying with the Bone Hunters before passing out. He was taken into a secret chamber of the Great Beings, where Berix managed to heal him. After recovering, he asked Mata Nui to help him acquire some new weapons. Mata Nui however, used the Kanohi Ignika to transform Gresh's blades and gave him the elemental power of Air.
While traveling to Tesara, Gresh practiced with his new powers. This inspired Kiina to blast away a nearby rock with her power, Water. Ackar then battled Kiina with his power, Fire. It was a standoff until Gresh blew both of them away with his new blades. After such practice and lessons, they arrived in Tesara. Ackar called for an end to the arena system, and urged the villages to unite against their common enemy of the Skrall and the Bone Hunters.
Later, Metus approached and informed the Glatorian that the Bone Hunters had kidnapped Kiina and Berix. Gresh offered help out Mata Nui, but Mata Nui insisted on going alone. He later joined the party that traveled to Roxtus to battle the Skrall. He encountered the massive army of Skrall and Bone Hunters, and began fighting them. Kiina, Ackar, and Mata Nui joined the fight, and they were able to combine their powers to finally defeat their attackers.
After the Battle of Roxtus; Gresh, Kiina, Berix, and Ackar later visited Mata Nui, who was supervising the construction of the unified city. Mata Nui thanked Gresh and the others for their support in his struggles. Gresh joined the defence force of the city under the command of Ackar.
Mata Nui attempted to lead a group consisting of himself, Kiina, Gresh and Berix to the Valley of the Maze, though they encountered a Skrall patrol along the way. Berix was injured in the fight, and Mata Nui insisted on making the rest of the journey alone. Gresh and the others returned to the city after the event.
After the conflict with the Skrall, Gresh salvaged new silver blades and new armour.
Later, Teridax, still possessing Mata Nui's giant robotic body, landed on Bara Magna to try to kill the Great Spirit. Gresh found an entrance to the robot on its foot and opened it, accidentally letting several Rahkshi of Heat Vision out. He also saw another being escape and attacked him, thinking it was an enemy. However, it turned out to be the noble Takanuva, Toa of Light. They soon realized they were on the same team and met up with Tahu. Gresh later retrieved a piece of the Golden Armor from two Skrall. After a long, heated battle Gresh then witnessed the Golden Armor activate and destroy a legion of Rahkshi. This caused Teridax to become distracted, giving Mata Nui an opening to shove Teridax into an Aqua Magna fragment and reform Spherus Magna. Gresh also witnessed Mata Nui deactivate himself.
He is now living on Spherus Magna after Teridax's death.