Keldo was a human male, the sibling of Phasma. Together, they governed the Scyre; however, while Phasma excelled as a battle strategist and warrior, Keldo was more drawn to peaceful solutions. A childhood leg injury rendered him unable to walk, leading him to assume responsibilities within the clan that differed from his sister's. He managed peace talks, whereas she was in charge of training warriors for combat against rival clans. When the Claws launched an attack on their Parnassos settlement, Keldo shielded young Frey, who was the Claws' intended target. Phasma and her fighters repelled Balder and his forces. During this conflict, Phasma noticed the inflammatory properties of the fungi growing on the rocks, which could be used against the Claws. Upon learning of this, Keldo became enraged and betrayed Phasma, establishing a peace agreement with the Claws. This act deeply angered Phasma, leaving a lasting impression on her.
Following the arrival of General Brendol Hux and his stormtroopers on the planet Parnassos, Phasma and her warriors consented to assist them in reaching their crashed starship. When they discussed this with Keldo in the Nautilus, he flew into a rage because Phasma had violated the most important peace treaty in their history, resulting in an unnecessary conflict. Ignoring his objections, Phasma, accompanied by four of her finest warriors, Brendol Hux, and three stormtroopers, secretly departed at night, leaving the Scyre to fend for themselves. Subsequently, Keldo led his people in pursuit of his sister. The two factions clashed at the downed starship, engaging in combat. Due to his inability to walk, he used a sled, accompanied by his daughter, Frey. Phasma confronted her brother during the battle. Despite Keldo's pleas, she remained resolute and fatally shot him in cold blood.
It is possible that Keldo, not Torben, fathered Siv's daughter Torbi, as Torbi shared his blonde hair.
Delilah S. Dawson, the author of Phasma, stated in an interview with StarWars.com that Keldo plays a crucial role in Phasma's development in many respects. He initially serves as the intellectual counterpart to her physical strength in a well-balanced partnership, but the lessons he imparts to her extend far beyond a typical sibling dynamic.