ALTERNATE VERSIONS
In the reality shown in What If (2nd series) #106, the X-Men were not as forgiving as in the main universe when it came to Gambit's involvement in the Mutant Massacre. Shortly after Marrow had joined the team, the X-Men were hunting down Gambit to decide on his final punishment for his deed.
Eventually, it was decided on the matter being solved in Morlock style, considering that the underground community had lost most because in the massacre. It was to be a duel, the winner deciding the loser's fate. Actually, Marrow was the only Morlock present and, as such, had the right to fight Gambit, but she refrained from participating in the duel in favor of Archangel, who had lost his original wings in the massacre. Gambit didn't want to have any further deaths on his conscience, so he didn't fight back, and Archangel couldn't bring himself to kill the Cajun X-Man. Marrow didn't have such quarrels, though, and rammed one of her bone daggers in Gambit's chest. With his dying breath, Gambit asked the X-Men to forgive Marrow, hoping that they could break the cycle of violence.
Marrow's counterpart of the Age of Apocalypse led a rather miserable life as well, her never even joining the X-Men.
Like many other mutants not deemed worthy enough to serve Apocalypse, she was an inmate of Sinister's breeding pens, held like a caged animal. After Magneto's X-Men ended Apocalypse's rule, Marrow and many other Morlocks returned to the tunnels underneath New York's sewers. They didn't trust any outsiders, not even the X-Men when they ventured into Morlock territory, inviting them to come and live with them in the surface world. Marrow feared they would end up in cages sooner or later again, and started a fight with the X-Men so that they would leave them alone.
In the Ultimate universe, Marrow was among four mutants that Sinister killed as part of a task given to him by Apocalypse.
It turned out that Sinister had merely been talking to himself, but by killing the young mutants and then dying himself he was able to transform into Apocalypse.
When Apocalypse merged with Cyclops during the saga of the Twelve, he used his newfound powers to warp reality numerous times. In one of them, various X-Men were re-imagined as members of Magneto’s Brotherhood. Marrow was the obvious analogy of Toad as she possessed his grotesque, hunched appearance and costume. In another reality, Marrow and Gambit were married and had produced numerous children, who in turn were having children of their own. Rogue had left the planet years before but, when she returned, Marrow became jealous when Rogue set her sights on Gambit once more. In the end, it was revealed that Apocalypse was warping realities in a bid to trick the X-Men into using their powers and charging up a machine that would make him omnipotent. With Apocalypse eventually stopped, reality was returned to normal.
When Legion warped reality and created the Age of X, Marrow was one of many mutants being kept at a prison camp. When a breakout occurred, a team of specialists put together by the government was sent. Lethal force was authorized and many mutants were killed. Marrow was almost killed by Redback, the AoX version of Spider-Woman. Susan Storm saved her but Marrow paid her back by knocking her out when her back was turned. Marrow was nearly killed a second time by Ghost Rider but was again saved by Chamber. In this reality, Marrow still seemed to possess her mutant powers.
In the House of M reality, Marrow was a member of Magneto’s Red Guard under the watch of Wolverine and Sebastian Shaw. When the Guard was sent after the Masters of Evil, Marrow managed to kill the Sandman once Rogue had stolen his powers. However, she was soon killed by The Hood in retaliation.
In the Battleworld domain of K’un Lun, Sarah was a part of a group of outcast who were forced to live in the sewers. Whilst all the other powered individuals belonged to prestigious fighting schools, none of them saw the value in Sarah’s bone growths and refused to accept her. When Shang Chi, the Emperor’s exiled son, returned to K’un Lun the outcasts took him in and taught him about themselves. They convinced him to enter a fighting tournament that would determine who the new Emperor would be. Thanks to the lessons learned off Sarah and the other outcasts, Shang Chi prevailed and became Emperor of K’un Lun. Afterwards, Sarah was allowed to take her place alongside Shang Chi and the other outcasts as he ruled the domain.