Leech is a fictional character appearing in American comic books published by Marvel Comics.
 Leech made his first appearance in Uncanny X-Men as a Morlock, a group of mutants whose deformities force them to live in the sewers under Manhattan. He is usually depicted as being around twelve years old (his exact age is unrevealed). He speaks in broken English and refers to himself in the third person.
 Leech first appeared in The Uncanny X-Men #179 (March 1984), and was created by Chris Claremont and John Romita Jr.
 Leech appeared as part of the "Morlocks" entry in The Official Handbook of the Marvel Universe Deluxe Edition #9.
 The green-skinned Leech was orphaned as a toddler. His parents left him to die when his mutations became apparent. He was found by the Morlock Caliban and taken to a human-looking mutant woman named Annalee who raised him and several other young mutant orphans as her children. He made friends with X-Factor's ward named Artie Maddicks and had a few brief encounters with the X-Men.
 During the Mutant Massacre story arc, Mister Sinister rallies his henchmen, the Marauders, to infiltrate the sewers and massacre all the Morlocks living there in an effort to rid the world of "genetically impure" mutants. While many Morlocks are killed, Leech and Caliban survive, rescued by Power Pack and the X-Terminators (X-Factor in their role of mutant hunters). Leech joins Artie in the care of X-Factor until they could be enrolled in St. Simons, a private school that willingly accepts mutant children.
 Soon after they began attending this school, Leech and Artie are captured by mutant-hunting demons. Leech's technologically enhancing mutant friend, Taki Matsuya and an ad-hoc team of mutants, calling themselves the X-Terminators, join with the New Mutants in battling the demonic threat. They adventure through much of New York, witnessing much, such as innocent men being eaten, before the threat is contained.
 Leech, Artie, and Taki return to St. Simons, though they do not stay out of trouble. Taki's crush on a teacher leads to uncovering a plot by mutant-hating humans to kidnap and kill as many mutants as possible. The young trio disobey orders and literally fly off. After much violence, the kidnapping plans are discovered and the conspirators arrested. A nearby resident, Ida Fassbender, discovers the trio's technologically assisted jaunts, and her paranoia endangers their lives. She resolves the problem and unofficially becomes the boys' grandmother. Leech is comforted by Ida's resemblance to Annalee.
 Another kidnapping plan works successfully and Artie and Leech are taken by the murderous mutant terrorists Gene Nation.[volume & issue needed]
 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 forebears. 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.
 Leech and Artie continued to live in the Massachusetts Academy under the care of Emma Frost and Sean Cassidy. They are later joined by Franklin Richards, who stays at the school while suffering from the loss of his family. Their friendship has unexpected benefits, as Leech is able to control Franklin's powers when they, aggravated by his grief, go out of control.
 The three visit the farm belonging to Hank McCoy's parents. Back at the Academy, they encounter Howard the Duck and other allies and as a group, are attacked by Black Tom Cassidy. Howard risks his life to save them all, then they are taken away by the Man-Thing. Leech and the rest have several adventures as the team called the Daydreamers. When Richards' family, who had previously been exiled to an alternate universe (see Heroes Reborn), return, the group was disbanded. Leech and Artie go back to the academy and take on more active roles.
 Soon after, the school became bankrupt, and Emma and Sean were forced to open the school to human students. To keep Artie and Leech from being isolated, Emma gave them both an image inducer in the form of watches. The boys were quick to abuse this new technology, and were quickly set straight by Emma. Soon after, the school became exposed as a home for mutants, and Artie, Leech, and Penance were all sent away to protect them from any possible dangers that might arrive.
 At some point, Leech is captured by the revived Weapon X program and was used by the Weapon X program to keep imprisoned mutants under control.  When the program was about to be discovered, those responsible attempted to erase all information surrounding it by killing the prisoners. Leech survives and is one of the estimated 198 mutants who retained their powers after M-Day and moves to an encampment in the Xavier Institute.
 When an exploding supervillain causes the general public to turn on superheroes, Domino, Shatterstar, and Caliban break out the 198 and take them to a bunker in the middle of the desert. They are sealed inside with nuclear weapons that are activated for self-detonation, but they are eventually freed from the bunker. Leech accompanies Caliban down to the old Morlock tunnels where they are attacked by an extremist group of Morlocks led by Masque, who after knocking out Caliban, kidnaps Leech because he needs Leech's powers. He is then rescued by the X-Men and Skids.
 Leech and Artie Maddicks were invited to Franklin Richards's birthday, and as a gift, Franklin invited them to live with the Fantastic Four. The two are now in a special class with intelligent moloids, Alex Power (Zero-G) of the Power Pack and other gifted kids. It is later revealed that Leech's cancelling powers were the reason that Reed Richards wanted him to be with Franklin. Leech later joins Reed's new Future Foundation superhero team.[volume & issue needed]
 Leech can dampen or completely suppress, for an undetermined amount of time, the powers and abilities of any superpowered beings within 50 feet of him. His dampening ability in the beginning was involuntary and uncontrollable, but now his ability appears to be under his conscious control. Leech explained to Johnny Dee he could consciously bring his dampening field in close, so that persons are not dampened unless they touch him.
 Leech has also been shown to dampen abilities that are non-mutant in origin at times, like the Fantastic Four, Hazmat of the Avengers Academy, and during Marvel's Mutant Massacre crossover event, Leech negated the powers of the superhero team Power Pack, whose abilities were bestowed on them by an extraterrestrial.
 In X-Men: the Animated Series, Leech was shown to possess telekinesis when he stole fruits from a fruit stand and moved humans that were in his way when trying to escape.
 When his ability has been targeted at mutants with super strength, at times his victims have become temporarily thin and frail.
 During the Age of Apocalypse, Leech is among the featured Morlocks that are survivors of Mister Sinister's experiments.
 Leech was introduced to the Ultimate Marvel Universe in Ultimate X-Men #82 as a member of the Morlocks. He was never shown using his powers, so it is unclear as to whether or not they are the same. He looks similar, but more like an old man than a child. He was shot and killed by Sinister in issue #90.