The green-skinned Leech's early history is unknown. He was a rare mutant whose physical mutation became apparent before reaching puberty. Leech was found by the Morlocks and raised as part of their underground community in The Alley. Leech was kept in close proximity to the Drain Dwellers Morlock group after Annalee lost her children to attackers. Annalee was a projecting empath, and her depression would affect her neighbors if Leech wasn't around to cancel her powers. Leech sought affection from Annalee, but she initially rejected him for being so ugly. With the encouragement of their friends in Power Pack, however, Annalee finally warmed to Leech, and he began calling her "mama".
The Morlocks were being massacred by the Marauders, and Leech, Caliban, and Artie were terrorized by Sabretooth, but they were saved by X-Factor. Leech and Caliban were separated from Artie and, while many Morlocks were being killed, were rescued by the Power Pack and the X-Terminators (X-Factor in their role of mutant hunters). Power Pack informed Leech that Annalee had been among the murdered and Leech and Caliban were taken to the X-Factor Complex by Beast and Iceman.
After the massacre, Caliban and the remaining Morlocks decided that they should return to The Alley and Leech and Artie parted ways. After Beast tried to help them reconsider, Masque attacked him and horribly disfiguring his face, until Caliban, with Leech negating their powers, beat him and made him change it back.
After hearing of Angel's apparent suicide, Leech and Caliban attended the funeral and returned to the X-Factor Complex. Leech, Artie, Rusty, and Skids were among the first to notice X-Factor PR man Cameron Hodge's devious acts, as they walked-in on a conversation he was having with The Right. After being tricked, by Hodge, into believing that Marvel Girl, Phoenix, and Madelyne Pryor-Summers were one and the same, Cyclops battled Marvel Girl and removed his visor in front of her, only to have Leech save him from destroying her. The children of X-Factor were captured by The Right to be used as weapons and learned that Cameron Hodge was the Commander, until X-Factor rescued them. 
Living on Ship
After their defeat of Apocalypse, his Ship crash landed on their Complex and X-Factor began living on Apocalypse's sentient Ship. It had a barrier only mutants could enter, and Caliban left with Apocalypse. After the children were given Christmas gifts as donations, they decided to give them to the children who lost their homes during X-Factor's battle. While sleeping, X-Factor and the kids were attacked by Ship, still under the control of Apocalypse, until Rusty freed its consciousness. X-Factor expelled a bomb and Ship, now able to speak, asked to join them. Ship had complete control over every part of its structure and could fashion rooms, weapons, and vehicles as needed from various storehouses and parts it had. Ship was able to design and run training programs for X-Factor, as well as make living quarters and workshop areas for them. While playing around on Ship, the students ran into Beast, who was going over old photos of X-Factor in their teens and revealed their origins, as the original X-Men and students at the Xavier's School for Gifted Youngsters. When the Xartans and Lord Zano, in Avengers disguise, attacked X-Factor, the children were protected by Ship, but later aided X-Factor. After finding that they were going to be sent to a private school, Marvel Girl and Iceman took the kids shopping for clothes, where they were attacked by the Alliance of Evil. After defeating the Alliance of Evil, Freedom Force showed-up and ordered Rusty and X-Factor to register, to which X-Factor accepted and Rusty turned himself into the Navy.
After seeing Rusty off at a Naval base, Artie and Leech went to a private boarding school, St. Simons, where they met another young mutant, Takeshi Matsuya (Wiz Kid). Soon after they began attending the school, Leech and Artie were captured by infant mutant-hunting demons. After being delivered to N'astirh, the demon was upset that Leech and Artie were not infants and they were held as motivation for N'astirh to bring back mutant infants. After the arrival of the former students of X-Factor, now calling themselves the X-Terminators, they were captured by the demons and everyone was teleported to Times Square. There the New Mutant, Magik, was opening a portal to return her teammates from the demon infested dimension of Limbo. N'astirh, using ten kidnapped mutant infants as the points of an inverted pentagram (focusing beams of power because of their purity and openness to use them as natural, living conduits who could not block the flow of power and who would not know how to shut it off), kept the portal open. Using clues from Taki, Leech and Artie powered-down the computer N'astirh used to keep the portal open and the X-Terminators bound, freeing the X-Terminators.
After Artie and Leech freed the X-Terminators, they joined the New Mutants in rescuing the infants being used to keep the portal open. Rusty suggested that the X-Terminators rescue their teammate, Taki, while the New Mutants continued to rescue the infants and disrupt the pentagram. After rescuing Taki, Leech watched over the infants, while the New Mutants searched for Magik. After the Inferno, the X-Terminators and New Mutants returned to X-Factor's Ship, with the mutant babies and Gosamyr.
The two went back to attending school for several months before they were kidnapped a third time, this time by Gene Nation. This group was composed of second-generation Morlocks, the descendants of those who survived the massacre in the tunnels. They were born and raised in an alternate dimension with a faster flow of time than this one, called The Hill. They sought revenge for those who wronged their forbears. The Gene Nation led a campaign to hunt down and kill as many humans as possible, since it was the humans' unwillingness to accept them that forced their parents into the tunnels in which they were massacred. Leech and Artie wanted no part of this, but were trapped until they were rescued by Generation X. They were thereafter made junior members and remained with the team for some time.
Leech and Artie continued to live at the Massachusetts Academy under the care of Emma Frost. When they met Franklin Richards, they were inducted into his own short-lived team, The Daydreamers. When Richard's family, who had previously been exiled to an alternate universe, returned, the group was disbanded. Leech and Artie returned to the academy to take on more active roles.
For a time, the academy was shut down and, although it was never made clear, Leech may have transferred to another school. He was eventually captured by the revived Weapon X program and forced into a machine that was designed to be attached to a mutant, take their powers, and then project them to any other mutant in the world. Sabretooth, then a part of Weapon X, used the machine at one point to strip Wolverine of his healing abilities in order to finish him once and for all.
Leech survived, but continued to be used by the Weapon X program to keep imprisoned mutants under control.
He eventually escaped, and after the events of M-Day, retained his powers and joined the 198 on the grounds of the Xavier Institute. In the 198 compound outside the mansion, the woman called Outlaw decided to look after him. Leech was mind controlled, via a puppet, by the mutant Johnny Dee in his attempt to kill Mr. M. Johnny Dee forced Leech to touch Mr. M thereby negating his powers so that he could then have Magma incinerate him. Instead of dying, Mr. M evolved into hundreds of butterflies.
Leech and Caliban went looking for a place to live in the Morlock Tunnels when suddenly a huge blast seriously hurt Caliban. Bliss came along and bit Leech with her poison. Later, Masque began to steal Leech's powers so he could find Magneto.
At Franklin Richard's birthday party, Leech and Artie Maddicks were invited to stay at the Baxter Building.
Leech also was sent to be with Hazmat for a short time, enabling her to visit her family and walk around normally. But for a while after Leech left, she was still powerless, unable to help Speedball and her peers during an attack at Stamford.
Following the foundation of a mutant state in Krakoa by the hand of Charles Xavier and his allies, Leech resurfaced as a citizen of the nation brought together by Xavier as part of his plans for mutant ascension. As part of the emerging mutant culture on Krakoa, Leech trained in The Quarry, where he won against Artie during Silver Samurai’s dojo.
Powers and Abilities
Power Negation: Leech can project a dampening field out from his body that disables any additional neural pathways found in the human brain, temporarily blocking access to any paranormal abilities (including: other mutations, extraterrestrial, magical, etc.) so long as they are within range of his field’s variable radius, which is approximately 10 yards. Some physical effects, such as being thin, may also occur depending on the nature of the powers that he negated.
- Leech used to speak in broken English, acting and speaking in the third-person. He recently demonstrated a better mastering of the English language.
- 171 appearance(s) of Leech (Earth-616)
- 6 minor appearance(s) of Leech (Earth-616)
- 4 mention(s) of Leech (Earth-616)
- 57 image(s) of Leech (Earth-616)
- 3 quotation(s) by or about Leech (Earth-616)