Gravity throne hologram
From Halopedia, the Halo wiki
File:DSC00183.JPG
Regret's lost throne.
This is a glitch in the level Delta Halo. Armed with a ghost, The_Delta_Halo_Vacation, and a lot of patience, you should be able to reach the end of the level. However, no honor guards will spawn and attack you, and the hologram prophet that Cortana translates, is gone. The Gravity Throne is still there. No idea why, but it's a glitch.The other hologram near the ruins is the same as this too.
Another method:
do the Floating Switch method. When you are on top, go near the center. You would be able to see the weird structure below. Jump down and if you land correctly, there would not be any guards and the Gravity Throne would be there without "Regret".
