Sebastian Shaw's power first manifested shortly after he was accepted to engineering school and his father died, when he was beaten by some rednecks in a bar. Shaw devoted himself to his studies and created Shaw Industries, becoming a billionaire by the age of 40. Shaw fell in love with a woman named Lourdes Chantel, and was soon initiated into the Hellfire Club along with Warren Worthington Jr., Howard Stark and John Braddock. Soon, Shaw rose to the position of Black King, and gathered mutant associates to his side, including Emma Frost and Tessa. Unfortunately, Chantel was soon killed by Sentinels in a battle. Upon discovering that Ned Buckman, the White King of the Inner Circle, was supporting Stephen Lang's Project: Armageddon and its Sentinels, Shaw executed a coup, using Emma's telepathy to make Buckman kill his own White Queen and then himself. Shaw then appointed himself Black King, and his associate Frost as White Queen of the Hellfire Club.

As the leader of the Inner Circle of the Hellfire Club, Shaw started plans to dominate the world through force, money and power. His connections to top officials of corporations and government, acquired via the club and through his position as CEO of Shaw Industries, made him a powerful enemy. Ironically, Shaw was for years a major supporter and builder of Sentinels, figuring that it was better to be in control of them than not. This activity brought him into frequent contact with Senator Robert Kelly and Henry Gyrich, to whom he appeared to be an anti-mutant human bigot. Secretly, however, Shaw continued his plans, some of which have involved Black Air and more recently, an unnamed group of time-manipulators.

Shaw was a key part of the corruption of Phoenix into Dark Phoenix, as well as the Hellfire Club's battle with the X-Men against Nimrod, during which he was thrown into the upper atmosphere by the future Sentinel, then caught by Harry Leland's gravity-altering power and slammed at phenomenal speed into Nimrod. Unfortunately, this effort had the result of killing Leland. Months later, Shaw was attacked by his own son Shinobi Shaw, who phased his hand into his father's chest to induce a coronary. Shaw was supposedly blown up in his Swiss Mountain chalet by a bomb set by his son. However, Shaw survived, though he was marked with a scar on his face crossing his left eye, since removed with plastic surgery.

Shaw's first move upon recovery from the bomb was to contact the man named Holocaust, who had crossed over from the "Age of Apocalypse". In exchange for a new armored containment suit, Holocaust agreed to help Shaw capture X-Force, which he did with frightful ease. Shaw then had Tessa reprogram X-Force to hunt down Cable, but Cable used his fledgling telepathy to break the conditioning and free his team. Shaw's association with Holocaust declined soon after.

Shaw's more recent exploits included vying for control of the Elixir Vitae, thought to be a cure for the Legacy Virus, and hunting down X-51, the Machine Man. Then, somehow, Shaw was apparently ousted from his position as Black King by Selene, who installed Blackheart in his place. This arrangement did not last long, as Shaw has since returned to power. He attempted to use Lady Mastermind to control Sage and the team of X-Men who were searching for the Destiny Prophecies. Then, after Professor X was "outed" as a mutant, Shaw apparently returned to his capitalist roots and converted the Hellfire Club into something closer to a real nightclub, but that was in fact a safe haven for mutants regardless of affiliation. Using telepathic dancers, Shaw gleaned secrets from the minds of his patrons, who came in just to have a good, decadent time.

After a few months, however, Shaw made a play to become the Lord Imperial of the entire Club worldwide, and invited Sage to help him. Sage accepted, but effectively betrayed Shaw when she didn't warn him that Pierce might try to assassinate him. Shaw met with the X-Men, claiming to be somewhat reformed, just before Pierce's attack. He was then wounded by Pierce, but remained strong enough to literally knock Pierce's head off. However, he was too hurt to maintain his Club position and was replaced by Sunspot, whom he had chosen as his Black Rook. Later, it seemed Shaw had joined forces with a new Inner Circle which included Cassandra Nova and Emma Frost, the latter of whom had since joined the X-Men. The Hellfire Club made their attack as they each targeted an individual member of Cyclops' team of X-Men. Shaw himself defeated Colossus. In the end however, it was discovered that the entire Hellfire Club was not real, and all were mental images created by Emma Frost's mind, which was infected with a special "programming" by Cassandra Nova in an attempt to revive her. The Shaw duplicate vanished. Shaw was one of the few mutants to retain their powers following M-Day. Shaw appeared incognito (disguised by an image-inducer) at a funeral for a mutant boy named Landru. Xavier overheard his thoughts of a possible coup against Sunspot during the service. When Shaw noticed him watching, he quickly created a Psi-Shield to hide his thoughts. When confronted by Professor X, he stated that he had only come to pay his respects.

Some time later, Shaw appeared at a Hellfire club dinner hosted by Sunspot and alerted him to a device left by his father that exploded elsewhere in the compound, resulting in the insanity of two club menials. Shaw asked his manservant for a file labeled "Cronus". After being upbraided over the explosion and deaths by da Costa, Shaw was ordered to investigate. Shaw, however, already knew the cause. The explosion in the Hellfire Club was caused by the activation of a machine developed beneath the Alamogordo genetics plant in Las Cruces, New Mexico by Mr Sinister. In the past Sinister had worked there (disguised as a Dr Milbury) alongside Brian Xavier, Kurt Marko and Irene Adler, who had been gathered for him by Jacob Shaw, Sebastian's father, as they all had the X-gene and Sinister predicted their children would be mutants. Sinister then experimented on these children (including Cain Marko, Charles Xavier and Sebastian himself), imprinting himself on their DNA. Sinister's machine, dubbed the Cronus device, was designed to activate soon after his death and would activate these hidden copies until Sinister could be reborn in one of them. Jacob, wanting to protect his son, created the device in the Hellfire club from Sinister's notes to alert and protect Sebastian from the Cronus device.

Shaw traveled to New Mexico to visit another of the children to confirm his theory, running into Xavier and Gambit, who were investigating a hit list with the children's names on it. Following them, he was present when they were attacked by mercenaries under the employ of Amanda Mueller, a former associate of Sinister. Xavier was captured and Gambit and Shaw teamed up to save Xavier. It was revealed that Mueller wanted to house the powers (though not the personality) of Sinister herself and so was assassinating the children, having undergone the procedure herself. She shot Xavier, who was already struggling to stop Sinister from taking over his body, which allowed him to take over. Sinister in Xavier's body stopped Mueller, but was in turn confronted by Shaw and Gambit, who destroyed the Cronus device while Xavier cast Sinister out of his mind. With the threat gone, Shaw left.

Since then, Sebastian has travelled over the world, and at one point found nearly permanent refuge upon the Pacific Islands, and stayed there for years, eventually discovering an elixir which would slow down his aging process as well. He acted like any other aristocrat, looking for the beauty of the wild far away from the urban world. Even during the cataclysm, he ceased to pick any allies, nor participate during the war, letting him live on in peace, not worrying about the fate of his old comrades.

Though, as soon as Elvira Slayer, who revived the Hellfire Club, and became the first Baroness Imperial of the house, he soon found himself intertwined with the Club once more. Elvira was looking for someone to join her ranks from the old club, so they could guide the club, yet not lead it. She saw the perfect opportunity when she found out that Sebastian Shaw was still alive and well, and after extensive research, she found his location, and pinned him down. Sebastian found her offer irresistible, glad to hear that the club practically fell apart with him gone. He also liked the new way the club worked as well, and had complete faith in its goals, so, he became its Advocate of Guidance. He also found himself in Her Majesty's Government, working for The National Archives.