Origin 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 saved by
Gambit, who was then 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.
Gene Nation 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.
X-Men 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. 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
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. The change of her features led to major softening of her personality, to the point where she reached out to
Jubilee following Wolverine's disappearance in the lead up to "
The Twelve" storyline. She also tried to cheer up returning X-Man
Colossus in a scheme involving his artwork and her storytelling. Marrow left the X-Men during the six-month gap preceding the "
X-Men Revolution", though her reasons for doing so are unclear. She was next seen brainwashed by
S.H.I.E.L.D. under the alias of "Sarah Rushman" used as a sleeper agent. Her mission was to terminate rogue
Life Model Decoys. She had a split personality (mutant Marrow and human teenager Sarah) and had to be periodically injected to keep her
implanted memory. With Spider-Man's help (he briefly dated her Sarah personality as
Mary Jane was believed dead at this point), she freed herself from S.H.I.E.L.D.'s control by faking a suicide.
Weapon X Marrow was later recruited by the most recent incarnation of
Weapon X, who again normalized her appearance and her powers. However, she eventually betrayed Weapon X upon discovering their anti-mutant nature. She used the remnants of Cable's Underground to reform the Gene Nation terrorist group and, as their leader, led several terrorist attacks on Weapon X until the rest of the group was slaughtered by
Agent Zero. Agent Zero left her alone, not wanting her to become a
martyr, but he warned her that he would come after her again after he had hunted down the remaining members of Gene Nation.
Decimation Marrow was next seen as a spokeswoman of a band of Morlocks after
M-Day. She gave an interview to
Sally Floyd for her ex-mutant diaries. Marrow remains underground to protect and give hope to the few mutants who remain and those who fear going to the surface to live normal lives. Mike Marts, editor for the X-Men comic books, confirmed in an interview that although Sarah retains some of the physical attributes of her mutation, her powers were lost during Decimation.
X-Cell Marrow later turns up as a member of X-Cell, a terrorist group of former mutants believing that M-Day was caused by the U.S. government. As part of X-Cell, Marrow fought
M and
Siryn of
X-Factor Investigations and after a turn of events in which she and Callisto learned the truth about who is responsible for M-Day, she turned against X-Cell supporter
Quicksilver. Both heavily injured each other with a knife wound during the fight. Afterwards, she and Callisto managed to escape X-Factor and the government through the sewers.
X-Force In Feb. 2014, Marrow returns as a member of a new X-Force team, along with a semblance of her powers intact. After some examination from
Doctor Nemesis, Marrow is revealed to be not a mutant. It has since been revealed that Marrow wasn't abducted at all. She willingly approached Volga, the one responsible for giving former mutants their powers back, for an experimental procedure to restore her power. At this point Marrow was already pregnant and despite the great risks this posed for her child, she accepted. The procedure was successful, and Marrow's powers were restored at the cost of her child, and she was left for dead in Alexandria during the Alexandria Incident. She was eventually found by Cable, who provided her with an inhibitor collar built by Doctor Nemesis to suppress her memories and control her powers.
Secret Empire In the
Secret Empire storyline, Marrow is affiliated with New Tian and fights along other mutants. Afterwards, Sarah joins Magneto's new Brotherhood of Mutants. She and others under his service attack an anti-mutant rally in Washington DC. Some time later she appears at a self-help group therapy session for mutants who suffered from debilitating appearances due to their abilities.
Disassembled After a massive reality distorting event caused by
X-Man had left much of the mutant population decimated once again, Marrow and a couple of other mutants work with
Emma Frost as debutantes in her new Hellfire Club. But they are soon beset by the
Office of National Emergency (O*N*E), now under command of the bigoted and corrupt Robert Callahan as part of his campaign of registering, incarcerating and modifying mutants for the purpose of exterminating other mutants. The duplicitous director coerces the Black King into tracking other mutants for his minions to round up in his government sanctioned facilities while under threat of execution. But Emma works with Marrow the others to contact the last remaining X-Men to deal with O*N*E.
Dawn of X Somewhere later down the line; after the new mutant nation of
Krakoa was established and declared its independence upon the world stage,
Professor X offers amnesty to all of mutant kind in the form of an invite to their personal island nation. Even the more socially abrasive amongst Homo Superior are welcomed amongst their growing numbers, as Marrow could be seen amongst an enclave of villainous mutants who accepted his summons. She is now a duly recognized citizen of the mutant nation. ==Powers and abilities==