During a pyramid run you must collect the following items:
a naos - in the room with the big crocodile, get naos niche
a solar disc - from the corpse of a crocodile-headed man
the mark of Horus - from the corpse of the 2nd cobra in the snake pit
the feather of Maat - from Khufu's sarcophagus
put the last 3 items in the naos, find the pharaoh's fleet.
follow self
sit hull
put naos niche
you will be transported to the secret chamber. stand up and walk out.