From Halopedia, the Halo wiki
Walkthrough: In the level Shutdown in the third spire. Get to the central platform with multiple light bridges. Cross the light bridge to the left of the bridge you would normally cross to reach your objective. This leads to a platform guarded by Jackals. The Terminal is located behind the platform's central column.
In a chamber with a holographic map of the Milky Way galaxy, red centers representing systems overtaken by the Flood.
A simulation of firing the Halos is run and the red systems fade out.
Shot of Requiem. In a Forerunner structure, the Didact falls to his knees, in anticipation. He has performed experiments on himself that have given him a much more sinister appearance
A holograph of Didact appears. A simulation of Flood infection is run and the form does not pass, turning red.
An armoured Promethean Warrior floats forward.
On the surface of Requiem.
The Prometheans, now digitized and changed into mechanized Knights, appear and surround him.
Camera pans back to reveal legions of Knights on Requiem.