Gram River is the central protagonist of the narrative, first encountered as a young man living on the floating city-ship of Adena. Abandoned or orphaned as an infant, he was left with only a mysterious necklace known as the "Mark of the Chief" as a clue to his past, and it is implied his parents held a significant status among the aboriginal people of Mars. He grew up fending for himself alongside a group of other orphaned children, including his close childhood friend Vestemona, surviving by stealing and taking whatever work they could find. After being adopted by a man named Mr. Lauren, Gram took on the responsibility of caring for the younger children, supporting them through a variety of odd jobs.

Gram possesses an athletic build and is a highly capable fighter and pilot, yet his true nature is that of a peace-loving and laid-back individual. He shows a clear preference for honest toil and cooking over combat, and his optimistic outlook often borders on reckless. This confidence, which can frustrate those around him, is exemplified by his willingness to use dangerous equipment like ice-booster skis without hesitation. His personality is grounded in a strong, almost stubborn, belief in others, refusing to believe that those he cares for would truly wish to harm him.

Throughout the story, Gram is propelled from a simple life into a much larger conflict after he falls into the ocean during a pirate raid. In the water, his necklace summons a mysterious and unique Round Buckler, which rescues him but is immediately mistaken by military forces as an enemy weapon. Forced to defend himself, Gram is ultimately accepted as a crew member of the pirate ship, the Ship of Aurora, where he quickly endears himself to the crew by taking on the vital role of the ship's cook. His motivations are rarely selfish; he acts to protect his friends and is drawn into the search for the "Stone of the Gods," a legendary artifact tied to his necklace.

His most significant relationship is with Vestemona Lauren, his childhood friend who becomes a military officer. Their reunion is fraught with tension as she disapproves of his new life as a pirate, leading to a chase through the streets of Adena and a confrontation where he kisses her before rejoining his crew. Their bond is later tested in a duel, where Gram arrives unarmed, not to fight, but to return a memento, allowing Vestemona to confess her true feelings and begin the process of reconciliation. Other key relationships form with the crew of the Ship of Aurora, where his skills as a pilot and cook make him an invaluable and trusted member.

Gram undergoes a significant journey of self-discovery, learning the true nature of his heritage when he visits the Mars aborigines and is given the Box of Guidance to find the Stone of the Gods. He faces betrayal, duels powerful mercenaries, and plays a central role in rescuing his shipmates from execution. By the end of the series, after the Ship of Aurora is severely damaged, Gram demonstrates his enduring hope and leadership by recovering a large derelict vessel from an ice graveyard. He names this new ship the "Ship of Hope," setting sail with Vestemona and two children to start a new chapter, his character arc concluding a transition from a drifting orphan to a decisive captain of his own destiny.

In terms of abilities, Gram is exceptionally competent both inside and outside of a cockpit. His varied work history, which includes stints as a circus performer and a heavy machine operator, has made him a skilled hand-to-hand combatant and an intuitive, talented pilot of his unique Round Buckler. He is also a proficient cook, a talent that serves as an immediate and practical contribution to the pirate crew.