From Destinypedia, the Destiny wiki
A large group of Cabal are waiting. The Guardian eliminates them, and heads inside.
The Guardian finds an old computer terminal and sends Ghost to investigate.
When the Guardian arrives at the Dust Palace mezzanine, several Legionaries and Psions attack from the first floor.
After defeating the platoon, they find an elevator shaft underneath the staircase. The Ghost opens it, and the Guardian drops down to the bottom. They reach a research station, littered with dozens of dead Fallen spread across the room.
More Cabal appear, and the Guardian takes them out.
The Ghost scans the computer the Cabal were guarding.
A rumbling is heard.
A few dozen Cabal soldiers, led by Centurions and a Colossus, attack the Guardian from all sides. They are all eliminated, and the hall runs quiet.