Marrow Real Name:  Sarah
Height:  6'
Weight:  Unrevealed
Hair:  Purple
Eyes:  Pale Blue
Mutant Powers:  Sarah's physiology is radically different from the norm.  At one stage she had two hearts, the second of which continued to function after the first was removed.
    Many of her bones grow to an abnormal size, protruding from her skin without causing her any real damage.  These bones are often blade shaped, and Marrow can use them as throwing or hand to hand weapons.  Once the bones are removed, new bones grow in their place.  Marrow has demonstrated that with extreme concentration, she can control the growth of these bones.  Her entire skeleton has enhanced durability, granting her some degree of protection against physical impact.
First Appearance:  Uncanny X-Men #325
History:  Marrow's physical appearance forced her to hide in the sewers with the Morlocks as a child.
    Marrow survived the Morlock Massacre due to being rescued by Gambit.  She was later taken to another dimension by Mikhail Rasputin along with a number of other Morlock children.
    Time passed faster in this other dimension, and she returned a few years later as an adult leading Gene Nation, the grown up Morlock children keen for revenge for the massacre of their people.  Gene Nation kidnapped a subway car full of humans on the anniversary of the Morlock Massacre, intending to murder one human for every Morlock that had died that night.  The humans were rescued, and Marrow faced off against Storm.  Marrow had attached a trigering device for explosives to her heart, telling Storm the only way to stop the bomb was to stop her heart.  Storm tore Marrow's heart from her chest in order to end the battle. 
    It was later discovered that Marrow's mutant body had granted her a second heart.  Marrow later resurfaced during Operation:  Zero Tolerance, meeting up with Iceman and Dr Cecilia Reyes, subsequently joining the X-Men.
    In a recent sojourn into another dimension, Marrow was injured by a wayard explosion from one of Gambit's cards.  Gambit took her to a hospital on the Skrull homeworld, although unable to completely understand the technology, Gambit did his best and Marrow emerged with her bone extrusions under control.  She has recently discovered that with extreme concentration, she can pass herself off as "normal".  There  also seemed to be a certain chemistry developing between Marrow and Colossus.
    Marrow has recently left the X-Men for reasons so far unexplained.