Leland possessed the ability to increase the gravity of an object or person within 350 feet of him, making it extremely heavy. Leland's power could affect both people and inanimate objects, but active resistance by the subject made it more difficult to assert Leland's power. Leland was overweight and in poor health, and thus he was a poor hand-to-hand combatant.
Little is known of Leland's past before encountering the X-Men, however he did encounter former teammate, Emma Frost before she was inducted into the Hellfire Club. At the time, Emma was homeless and using her powers during a Hellfire Club meeting to gain information about stocks, Leland took an interest in her but came on too strongly, which made Emma run away. Shortly after, he accompanied Sean Cassidy and his NYPD partner to an incident behind the club which involved Emma. Emma, having met and repaired the fractured mind of the Dark Beast with her powers, mind-wiped all three men into forgetting the incident and that they had ever met.
Later, Leland first encountered the X-Men when the X-Men invaded the New York headquarters of the Hellfire Club. Leland caused Wolverine to become super-heavy and fall through the floor into a sub-basement. In the rematch, Wolverine attacked Leland from above. At that moment, Leland foolishly used his gravity-increasing powers against his opponent a second time, resulting in Wolverine crashing through the floor again, only this time with Leland beneath him as Wolverine intended. All evidence to the contrary, Leland survived this incident.
Alongside the Hellfire Club, Leland later battled the X-Men in New York's Central Park. Leland used his power to sink Colossus hundreds of feet underground. When Nimrod attacked the assembled mutants, the X-Men and the Club joined forces to battle Nimrod. Against considerable resistance by the robot, Leland increased Nimrod's gravity to move it towards the ground and thus vulnerable to attack. Overweight and in poor health, the effort caused Leland to have a heart attack. Then, at Storm's urging, Leland increased the gravity of Sebastian Shaw (who had been sent hurtling towards outer space by Nimrod), causing Shaw to crash into Nimrod's body on the ground. Leland succumbed to his heart condition and died.
When the supervillain Black Talon revived Leland's body, as well as the bodies of three other deceased mutants, as a zombie; his motives for doing such were unspecified. After She-Hulk's defeat of the Talon and his "X-Humed", Leland was reburied. Precautions were taken to ensure that he never come back, among them filling his mouth with salt and sewing his lips together.
* Artist John Byrne based Leland's appearance on actor-director Orson Welles, and the name refers to two characters in Welles' films: Harry Lime from The Third Man, and Jed Leland from Citizen Kane. * Shinobi Shaw has speculated that Leland is Shinobi's biological father, but this has not been confirmed in canon.