Marrow
Real Name: Sarah
Affiliation: Gene Nation, (Former) Weapon X, X-Men
Height: 6'0"
Weight: Unrevealed
Eyes: Blue
Hair: Purple

Marrow is a mutant whose physiology has radically altered from the human norm, at one point she possessed two hearts. Many of Marrow's bones grow to an abnormally large size and protrude from her skin without causing any physical damage to herself. Once Marrow has removed any of these bones, new bones grow in their place. Marrow's entire skeleton has enhanced durability.

In our reality, Marrow hid herself as a young girl in the sewers underneath New York City as a member of the Morlocks, a group of mutants who were also physically deformed. Marrow managed to survive the Morlock massacre by the Marauders and was later taken, as a young girl, to another dimension by the mutant Mikhail Rasputin in order to survive the destruction of the Morlock Tunnels. Time passed quicker in the other dimension, and Marrow returned a few years later as a full-grown adult leading Gene Nation, a rebel faction of Morlocks who wanted revenge for the massacre. Marrow later resurfaced in New York in order to stop the Prime Sentinels of Operation Zero Tolerance when encountered the X-Man Iceman and the mutant Dr. Cecilia Reyes, and subsequently became a member of the X-Men.

020) The Skrull Colonies (Knock Out)
Appearances: 8, 9, 10
We got to see this world's Marrow be defeated by Nocturne during a bout in the Games. After the Skrulls departure, Sarah partook in the battles against both the herald Terrax and his master, the world devouring Galactus.