You decide what happens next.
The Master Chief walked through. He heard something. He turned around, and slipped, his Battle Rifle falling out of his hand, then he started sliding down a large arch, an Ultra Elite Duel Wielding Swords running to him. He Grabbed his pistol, and tried to reach for his rifle at the same time, when he hit the floor. Then the Elite prepared to strike and.... YOU DECIDE, WHAT HAPPENS NEXT!?
The Ultra struck downwards, only for the Chief to grab his swords and wrestle them from his hands. The Elite then un-holstered a plasma rifle, only for his arm to be diced open. The Chief jammed the other through its heart, then set off down the hallway.