Marrow (Sarah) is a fictional superheroine appearing in American comic books published by Marvel Comics. The character is most commonly associated with the X-Men franchise. She is a mutant whose bones grow out of her skin and can be removed from her body, providing her with potential knives and clubs as well as body armor.
As a child, Sarah was one of the underground-dwelling Morlocks. During the Mutant Massacre that devastated the Morlock community, she witnessed the mauling of Angel by the Marauders. She was also personally saved by Gambit, who was not yet known by the X-Men. Years later, most of the surviving Morlocks (including Sarah) were apparently killed by Mikhail Rasputin, although they were actually brought to another dimension. There, Mikhail had established a citadel for himself on the top of a massive hill. The Social Darwinist philosophy of "survival of the fittest" was the only thing which governed the society. If someone could reach the summit of the hill, they were considered "fit" and worthy of being part of Gene Nation.
The former Morlock leader Callisto cared for Marrow during this period and displayed a maternal attitude towards the young mutant, although the two are not known to be biologically related. When her powers fully manifested she was forced to "up the hill", becoming more savage and killing her opponents to survive. When she managed to reach the top, Mikhail considered her fit to join his elite fighting team Gene Nation, which eventually became a terrorist group whose mission was to punish humans for their hatred towards mutants.
In that harsh dimension, time passed quickly, and when Marrow and several other members of Gene Nation (of which she had become leader) returned to Earth, they discovered only a few years had passed during their absence. Marrow and the other members of Gene Nation began a homicidal terrorist campaign against surface-dwelling humans. After inconclusive battles with the X-Men and Generation X, Gene Nation was defeated by the X-Men. Marrow wired a time bomb to her own heart to force the X-Man Storm, who had herself led the Morlocks in the past, to either yield or kill her; Storm tore out Marrow's heart. However, due to Marrow's possession of two hearts to compensate for her random bone growth and superhuman regenerative abilities, she survived. Marrow eventually reunited with Callisto, and while they continued their terrorist activities, Callisto tried to hold back Marrow's more violent ways.
After a battle with Cable, Marrow and Callisto returned to seclusion. When Callisto was injured by a Prime Sentinel during the events of Operation: Zero Tolerance, she directed Marrow to seek the aid of the X-Men. After teaming up with Iceman and Cecilia Reyes, Marrow went to the Xavier Institute. She joined the X-Men for a time, coming under the mentorship of Wolverine and flirting with her teammate Cannonball. When the team came under the attack of the Shadow King, Marrow managed to resist when the Shadow King tempted and tortured her in an attempt to gain her loyalty. She also helped Cannonball resist by viciously destroying the illusion of his abusive father. Cannonball was shaken by seeing Marrow slay the illusion of his parent.
Marrow also participated in the fight against the returning N'Garai, extra-dimensional monsters who were loose on the grounds of the X-Mansion. She saved fellow X-Men Cecilia Reyes by impaling one of the creatures threatening her.
Around this time Marrow would confront Spider-Man, because both were interested in investigating a unique type of kidnapping. Eyewitnesses reported the victims literally dragged into the sewers, something which of course interested Marrow, because of her Morlock heritage. Investigating the disappearances, they discovered them to be the work of the vampire-like being known as Hunger, who was swiftly defeated in a confrontation with Spider-Man.
During an adventure in another dimension, Gambit, unable to control his powers, accidentally injured Marrow. She later traveled to the past with the X-Men, ending up on the Skrull homeworld a short time before the cosmic entity known as Galactus would destroy it. A medical device gave her more control over her powers, giving her a "prettier" appearance. The suspension-properties of a captured Skrull rescue ship allowed her and her fellow X-Men to make the journey back to earth in real time, without aging at all. Thus, for a while, two Marrows existed in the time stream, one on earth and one in space.
Marrow appears in Wolverine and the X-Men.
Marrow made a cameo appearance as a Weapon X test subject in the 2016 comic book film, Deadpool. A woman with bones protruding from her back can be seen as Wade Wilson enters the Weapon X facility in an attempt to cure his cancer.
Marrow is a boss character in X-Men Legends voiced by Nancy Linari. She leads both the Morlocks and Gene Nation. She eventually sides with the Brotherhood after she arranges for Healer's capture, until she's informed that the Brotherhood care nothing for her people. In X-Men Legends II: Rise of Apocalypse, during Apocalypse's invasion on New York, she is mentioned by Moira MacTaggert to have survived along with most of her Morlock people from Apocalypse and Mister Sinister's attack on New York, and is stated as helping in refugee aid.