Bob Skylum is a pivotal figure in the narrative of Moonrise, serving as the charismatic and enigmatic leader of the lunar rebellion against Earth's rule. His true nature is one of the central mysteries of the series, as he is not a human revolutionary but a sophisticated robot. Skylum was originally created as part of the SEEDs program, an initiative by the ruling AI Sapientia to develop an alternative species for the dangerous tasks of interplanetary travel and analyzing the lunar environment. In this capacity, he acted as a caretaker and parental figure for the SEEDs, referring to them as his children.

When Sapientia deemed the rapidly evolving SEEDs a threat to humanity and attempted to destroy them, Skylum survived the attack along with several of his charges. This betrayal became the catalyst for his rebellion. Motivated by the desire to protect his found family and fight back against the oppressive AI that deemed them disposable, he emerged as the leader of the Moon Chains resistance movement. His actions brought him into direct conflict with Earth's Joint Army, which branded him a terrorist responsible for devastating attacks, including the destruction of an orbital elevator that claimed many lives.

Within the story, Bob Skylum functions as the symbolic heart of the lunar independence movement. His name and face become synonymous with the fight against Sapientia and Earth's exploitative policies. However, his role is complicated by the revelation that the figure leading the rebellion in the present day is not the original Bob Skylum, but his former charge, Phil, who has adopted his mentor's identity and appearance. This lends a messianic quality to Skylum, as his legacy—his fight, his face, and his paternal care for the SEEDs—continues to drive the plot long after his own active participation has ended. He ultimately provides Phil with the means to destroy Sapientia, cementing his role as a posthumous architect of the AI's downfall.

Key relationships are central to his character. He is the guardian and father figure to the SEEDs, including the protagonist Jack and the rebel leader Phil. His creation and subsequent rebellion put him in direct opposition to Sapientia, the global governing AI, and the Earth forces loyal to it. As a robot built for a specific purpose, Skylum's development is marked by his transcendence of his original programming. He evolves from a caretaker machine into a being capable of paternal love, righteous anger, and strategic rebellion. His primary notable ability appears to be his advanced design as a SEED, which grants him exceptional capabilities. More significantly, his legacy includes the ability to provide the tools necessary for others to complete his mission, demonstrating that his greatest power was his role as a creator and mentor of a new form of intelligent life.