Flying Rtas 'Vadum
From Halopedia, the Halo wiki
To see Rtas 'Vadum fly, kill all of your allies at the very beginning of the level, The Oracle on Halo 2, except Rtas 'Vadum. Then, go to the next room, kill the Flood Combat Forms and trigger the Holo-Drone. Right after it disappears take out Rtas 'Vadum's shield and lure the Flood Infection Forms to him. As more infection forms attack him he will begin to rise off the ground and sometimes fly straight up.
