Lucian Grey did not have a happy childhood. His father (Paris), a Guardsman, was a bully and tended to hit his wife (Joella), a food service tech, who psychologically abused both Lucian and her husband. As a boy, the only time his father was happy was while watching old football games, so little Lucian began to treasure those games as quiet times when his mother was just sniping around the edges, and he and his father actually had something in common.
As he grew up, his mother's torment grew worse, always belittling the boy and tearing down his every effort. Lucian grew closer to his father, for all that the man was a sadistic brute, because Paris offered some protection from Joella. This closeness caused Lucian to apply to be a Guardsman himself, becoming a Cadet at 14.
On one of his first training exercises, Lucian's father was killed in an accident, the compartment decompressing and Lucian himself just barely escaping before the pressure doors closed. Some Guardsmen blamed Paris' "brutish incompetence" for the death, while some blamed Lucian. Joella definitely blamed Lucian, and her torment of the young man grew ever more intense. Over the next two years, Lucian did his best to avoid and escape his mother's tyranny, making several friends and escaping to other sections of the Ark whenever he could. To this day he wears a braided bracelet on his left wrist that was given to him by one of those friends.
But he could only escape his mother so long, and as his Guard training took up more and more of his time, his mother restricting him even more tightly on what little was left of his time. Eventually, he could take no more of it, and one night, late into his sixteenth year, when Joella came at him too hard, screaming at him for some imagined fault, Lucian snapped. He took his Guard-issue shock baton and he lashed out at his mother. When he was done, Joella Grey was dead, and after a moment's panicked planning to cover the death up, he marched into the Guard offices and turned himself in. He was jailed before the night was through.
Inside the Skybox, he had some issues with his fellow inmates — after all, his father had arrested or hassled some of them, and he had been training to be a Guard himself. Some of those he solved rather physically, and some of them, well… he fell back on his mother's methods and just mocked his tormentors.
Despite his friction with many of the Delinquents, Grey has made a name for himself on the Ground. He was part of the group that brought back the first meat to the camp, and stayed out with the Delinquents who brought back the bodies of the boiled hunters. He's struck sparks with people on both sides of the Pro-Ark/Rebel argument, and on the Hold out/Resettle argument.
He was also one of the leaders of the ill-fated expedition to Mount Weather that saw two Delinquents dead and four more captured. He was one of the leaders of the strike to free the prisoners and capture Grounders of their own.
Although at first he was a strong proponent of keeping the prisoners as long as possible, after reconnecting with the Ark, he changed his tune. His status in the camp took a tumble when he engineered the release of the Grounder prisoners without consulting the camp as a whole, even though his actions led to the possibility of a peace summit with the Grounders. When elections were held to choose negotiators, his name was barely mentioned.
Grey was attacked by four Delinquents led by a troublemaker named Rawlins after the medical team had gone up to Coesbur. He managed to hurt all four of them, but they knocked him out and tied him to a tree, trying to blame the Grounders. With his bruises still healing, Grey led a group to the river between Coesbur and the Round Hill Caves, helping to kill the river snake living there.
When the second dropship fell to Earth, Grey headed first to Coesbur to inform Oxfor that it was an accident, not intentional, and then went east with the group that investigated the crash. Finding ruin, death, and angry Grounders, he came back with a nasty arrow wound in his right side.
Rumor has it that the Grounder woman who came to camp to help the Delinquents, the former prisoner Gideon kom Trikru, was sleeping in his tent and tending to his wounds. During the assault on the Camp, he tried to get the Delinquents to retreat over the wall and toward the recently-descended Ark, but ended up being one of the last into the dropship instead.
Missing being captured by the Mountain Men, Grey took up Chancellor Kane's offer to become a full-fledged Guard. He assisted the Trikru with the clearing of Coesbur, witnessing the missile strike, took part in the scouting mission to Mount Weather, and helped capture a Reaper. He was one of the major proponents of assaulting the Mountain to get their people back, and ended up leading one team after the Lieutenant in command was killed. In the major assault that followed, Grey was part of Major Wu's team assigned to shut down the power to the Mountain, coming through with a minor wound and another couple of kills.
Upon their return from the Mountain, Grey and Gideon started constructing a house for themselves in The Row, a cobbled-together combination of metal and wood construction.