Marisa O'Day

"You are Spartans when you graduate this program. And you graduate this program when I say so. Do you know what that means? It means you're not a goddamn Spartan until I say you're a goddamn Spartan! You might feel like a superhero, but right now you're as useless as a baby—and the UNSC doesn't need any goddamn babies!"

- Captain O'Day, to Spartan trainees

Captain O'Day was a human officer serving with the United Nations Space Command. By 2554, she was a drill instructor for the SPARTAN-IV program.

Biography
Captain O'Day served as a drill instructor for the second class of the SPARTAN-IV program. She was tasked with training the Spartans to break their bad habits that they had formed over the course of their military careers. In 2554, O'Day was stationed aboard an unidentified space station orbiting a dwarf planet. Spartans in one of her training groups included Edward Buck, Kojo Agu, Michael Crespo, Rudolf Schein, and Kovsky.

Unbeknownst to most, Schein was affiliated with the United Rebel Front. After a training exercise, Schein murdered fellow trainee Hideo Wakahisa and then set a series of explosives around the station. When it was discovered that Schein was responsible for the murder, O'Day, Jun-A266, and Musa-096 confronted him in the station's recreational room. Schein threatened to blow up the entire station unless his demands were met. When Schein attempted to detonate the explosives he had placed around the station, Jun charged at him and knocked the trigger out of his hand. Musa managed to turn off the station's artificial gravity, which caused the explosives' switches to falter and prevented all the explosives in the station from detonating. However, Schein still managed to prim a grenade. While O'Day attempted to avoid the explosion, she was caught in its blast and propelled down a hallway. The explosion knocked her unconscious and set her legs on fire. Buck, Agu, and Crespo grabbed her and left to bring her to safety. As they attempted to escape from the breached rec room, Buck and O'Day smashed into a door. Having hit the door at a bad angle and at a high speed, O'Day died instantly.

After Schein was killed by Jun and the situation ended, Musa contacted Buck, Agu, and Crespo told them to leave O'Day's corpse in the room they were taking shelter in. A clean-up crew came by later to remove her body.

List of appearances

 * Halo: New Blood
 * Halo Fractures
 * Lessons Learned