She was under the command of First Lieutenant Melissa McKay and headed one of her platoons of Marines. When the vessel was attacked over Installation 04, she, with the rest of her men, made the jump to the surface aboard a Human Entry Vehicle.
During the journey back to Alpha Base after raiding the Pillar of Autumn she staged a plan to take out the Banshees attacking the convoy. Lt. McKay did not know about her strategy, but Oros continued anyway. Oros' squad of ODSTs left their Warthogsto find cover in a clustered, rocky hill. They launched a surprise salvo of rockets at the wing of enemy Banshees approaching the convoy. All of them scored direct kills except for three surviving Banshees. The two broke formation and retreated while the third mortally wounded aircraft plunged into the rocks where Lieutenant Oros' squad was hiding, engulfing them all in a deadly explosion. All Marines, including Oros in the squad, were presumed KIA. If any managed to survive the banshees' suicidal feat, they would most likely have been killed either by the Covenant, the Flood, or the destruction of Installation 04.
- Oros was frequently slandered as an addict to chocolate by her fellow soldiers.
- Oros was referred to as both a man and a woman. This is most likely a mistake.
- Oros was described to have a pixie-like face.
- Halo: The Flood (First appearance)