Flechette

Marrow is a mutant in the Four Corners during 2253.

Background
Marrow was born in the settlement of Dayglow to two prospectors. As a child, they regularly brought her on their expeditions into the ruins of San Diego, also known as the Glow because of the high levels of radiation. After both her parents died of cancer in their forties, a sixteen year old Marrow elected to leave Dayglow so that she wouldn't face the same fate. She hitched a caravan east and has been working caravans as a guard ever since. She developed her mutation not long after leaving, and become a popular addition to any caravan due to her ability to take bullet and determination to never run from a fight. When the NCR-Brotherhood war made caravan life difficult, and dangerous, Marrow headed east into the Four Corners. There she was imprisoned by ODYSSEUS in Tibbet's Prison, the AI incorrectly believing that her mutation proved she had the New Plague. Marrow found herself in the worst, most disgusting cell on the blog, with it's number printed on the back of her jumpsuit: 76.

Qualities
Although it's unclear what caused her mutation, Marrow is certain it came after she was exposed to heavy doses of radiation, likely as a result of her frequent trips to the Glow. The result was greatly accelerated bone growth. Her bones are harder now, much harder, dramatically increasing her endurance and toughness at the cost of her agility and speed. However, they also continue to grow, splitting her skin and growing outside her body. This gives Marrow an unattractive, freakish appearance. She usually files these bone growths done or breaks them off. She uses the broken pieces of the longest bone growths as weapons. As a result, Marrow is talented at melee and unarmed combat.

Trivia

 * If Marrow was a mutant in Fallout 76 she would have the "Talons" mutation.
 * Marrow's increased bone density make her much heavier than a normal woman of her size.  As a result, she has difficulty swimming, and sinks easier in water, as her muscle size has not been increased to compensate.