Spartan-458 is a special guest character in Dead or Alive 4. Her background information included with the game indicates that her real name is Nicole and that she was born in the city of New Legaspi on Mars in 2531. She was scouted by ONI (the Office of Naval Intelligence) at the age of six due to her physical capabilities and was enrolled in the SPARTAN-II project, the same project that created John-117 and Jorge-52. Her rank within the military is petty officer second class. Nicole was created specifically for Dead or Alive 4 and is not considered a canon figure of the Halo universe.
Bungie explains that she was transported through time in the Nassaru orbital Station due to a space-time bubble caused by the ONI stealth ship Apocalypso when it was jumping to slip-space nearby. Her motivation in Dead or Alive 4 is to keep the Nassaru Station secret and protect it from invaders who might jeopardize history, until the space-time bubble collapses and the station (along with Nicole) is returned to the twenty-sixth century.
Originally, Team Ninja requested that Bungie allow Halo protagonist Master Chief to appear in Dead or Alive 4 as a guest character. Bungie denied the request, but through a compromise, Nicole was created instead.