Leech's family left him expecting him to die after his mutation manifested. He was then seen by Caliban and brought him to Annalee who took good care of him alongside with other mutants whom she raised. He became a young Morlock. He then befriended Artie Maddicks and had some encounters with the X-Men.
Leech was created by Chris Claremont and John Romita Jr and first appeared in The Uncanny X-Men #179 (1984).
Mayor Story Arcs
Mr. Sinister ordered the Marauders to murder lots of mutants including the Morlocks. Many have died during the encounter with Sinister's mutants, however, Leech and Caliban have been saved by the Power Pack and the X-Terminators. Together with Artie Maddicks, they have been taken into custody of the X-Factor. After the encounter, it took them some time and enrolled to St. Simons which accepted them despite their mutation.
The two have then been abducted by anti-mutant demons but were successfully rescued by Taki Matsuya's X-Terminators with the New Mutants. Takin, Artie and Leech have returned to St. Simons, though, they were abducted again by another group which called themselves Gene Nation. The Generation X then rescued them and took them to Massachusetts Academy.
Artie and Leech lived in Massachusetts Academy under the supervision of Emma Frost for long and have met Franklin Richards. Leech have took control of Franklin's powers when Franklin got out of control. They then met Howard the Duck and befriended him, as a team, were attacked by Black Tom Cassidy. Howard risked his life for the salvation of his friends, though, the latter were taken by the Man-Thing. Franklin have formed a team called the Daydreamers but have not lasted for long since his family ( Fantastic Four) have returned from an alternate reality. The two then returned to the Academy to continue their membership to Generation X.
When the Academy was already bankrupt, Emma gave Leech and Artie an image inducer which allows them to appear normal to the human eye and let them live a normal life. The two have abused this technology. When the real intention of the Academy (as a home for mutants) was revealed, the young mutants including Leech, Penance and Artie were sent to a safer place away from the Academy.
Leech was then taken by the Weapon X for the mission to transmit his powers to another mutant through the use of a machine. Sabretooth have used this machine for the attempt to block Logan's healing factor and kill him. The Weapon X have then been revealed and to be able to be safe from revelations, they killed anyone with the connection of Weapon X. Though Leech have survived from the usage of the machine, he was forced to stay with the Weapon X to take control of the mutant prisoners.
Leech was one of the mutants who retained his powers ( The 198). He reappeared in the Mansion from Neverland. Outlaw then decided to take supervision on him. Though, Leech have been successfully mind-controlled by Johnny Dee as his puppet. He used him in his attempt to kill Mr. M. Leech have negated his powers for Magma to do the next move. Although Johnny Dee succeeded, it was stated that Mr. M have not died but have evolved into butterflies.
Leech then joined Lorelei. As he was last seen. he is along with Caliban looking for a good place to live in the Morlock Tunnels. The two have then been attacked. Caliban was hurt by a blast while Leech was bitten by Bliss and injected poison on him. Before the Civil War, they ended up at the Xavier Institute and lived in the camps outside. The property was surrounded by sentinels and none of the mutants were allowed to leave freely. This was until Shatterstar and Domino came and freed them. Domino and Shatterstar were able to get to a safe location from Captain America's Anti-Registration forces on a place to hide the mutants. The mutants went to a nuclear test base. As the standoff between the X-Men and SHIELD over what should happen with the mutants, they were almost all killed by Johnny D and General Lazer. The combined efforts of the X-Men, Sentinels and some Avengers were able to get the the 198 out, but Cyclops powers were out of control. Leech was the one that turned off his powers and saved Cyclop's life.
He recently went to his friend Franklin's birthday party along with Artie, at the party he was given a key to enter the Baxter Building and an invitation to live with the "Fantastic" family as part of the Future Foundation. Artie has continued to live as a ward of Reed Richards and recently helped the Avengers Academy student Hazmat with the control of her powers. Leech was brought to the Academy on the suggestion of Hank Pym. Because of Leech, Hazmat was able to contain her powers and visit the outside world without her containment suit on. She was even able to visit her parents thanks to the power dampening powers of Leech.
Leech has the ability to negate any kind of powers no matter what its origin is, whether it is mutant or extraterrestrial power. Leech's powers were once uncontrollable and involuntary but as time passes by, he studied how to take control of this. His powers can also weaken powers and cause temporary depowerment. Some physical effects such as being thin may also occur depending on the nature of the power that he negated.
Relatives: Annalee (Foster mother, deceased), Unnamed parents who abandoned him (whereabouts unknown)
Weight: 67 lbs
Features: Leech has no nose
Others: Leech speaks broken English and acts and speaks in the third-person;
Leech always looks to be around 12 years old.
Legacy Virus Merged with Warlock (Earth-8545)
Leech is a member of the Avengers who helped the Exiles against the Vi-Locks.
Age of Apocalypse (Earth-295)
Leech is a Morlock who survived from Sinister's experiments, when Cyclops and Jean Grey released the prisoners of the Breeding Pens, the Morlocks returned to sewers in order have a peaceful life. A year after Apocalypse was defeated by the X-Men, Magneto offered to the Morlocks the opportunity to live in the surface and abandon their tunnels. But, their leader Marrow refused the offer and attacked the X-Men, thus the Tunnels became a battlefield, so Leech used his mutant powers to weaken the X-Men, nevertheless Storm attacked him and left him unconscious. The Morlocks were incarcerated and put under government custody.
Days of Future Past (Earth-811)
Leech is a child who hides along with Jubilee and Synch. However, he was captures by Baron Zemo and the Thunderbolts after Charlotte Jones said their location in Los Angeles.
X-Men Millenial Visions (Earth-1035)
In an alternate future, after a thirty-year war on mutantkind, Leech stands as one of the last four mutants remaining.
Days of Future Now (Earth-5700)
Leech was a member of the Ultimate Morlocks. It's unclear as to whether Leech's power are the same in this universe as the has not yet displayed them.
He looks almost the same, other than the fact that he now looks more like an old man rather than a child. He was shot and killed by Sinister in the end.
X-Men: Animated Series
Leech is suffering from a disease and to be able to survive, he need to have a blood transfusion with Wolverine and use his mutated blood with healing factor.
In the series, Leech is this characters' last name and not his codename. Leech is a young mutant who lives with his mother who always makes him believe that he is not a mutant though his mutation is obviously manifesting. He always watch news about mutants and was prohibited by his mother for his own safety. He always encounter migraines and accidentally uses his powers. In a shop, where he and his mother were used to buy something, Leech was bullied by the customers. Spyke then appeared to save him but it only caused trouble specifically to Leech's image as a mutant.
When the MRD have then appeared, the X-Men and some Morlocks appeared to face them. Leech's powers manifested and negated all powers around him including electric, kinetic and even the mutant powers of the X-Men. Cyclops have stated that his powers were also negated by Leech allowing him to show his eyes.
During the final battle against Apocalypse. Rogue was assigned a special mission under the command of Wolverine. Rogue appeared in the chopper with Leech whom she fetched together with his mother to assists him. With her touch, Rogue borrowed Leech's powers and went inside the Pyramid with Cannonball. She used Leech's powers to negate the machines that would allow Apocalypse to spread more evil. Apocalypse was then defeated.
X-Men The Last Stand
Leech was portrayed by Cameron Bright. Though he uses his codename Leech, he is often called Jimmy. He is said to have the cure for the mutant gene that will cause normality to mutants if they were cured. His mutation in the film is involuntary as he can negate all kinds of mutation. When Beast shook hands with him, his hand lost its fur.
For his safety from Magneto's attempt to kill him, he was sent to Alcatraz. When he is brought to the facility, Magneto's Brotherhood have attempted to kill him despite the X-Men's presence. Juggernaut looks for him as he slams every wall that he sees. Logan then assigned Kitty Pryde and raced by phasing through walls. The two assigned mutants have faced each other. Kitty buried Juggernaut through phasing but was able to come out because of his strength.
Kitty have seen Leech and attempted to phase to save him. Though, Leech's powers which composes the entire room disabled Kitty to phase. Juggernaut then appeared and attempted to smash them with his head, but as Leech's powers were still present, it removed his invulnerability and knocked himself unconscious.
Leech together with the X-Men Kitty Pryde and Iceman have evacuated from Alcatraz. He later enrolled in the Institute as he was accepted by Storm.