After a vision showing what's going to happen in the future, your task is to exit the main hall. If you got injured during the fight, you can drink from the water at the end of the hall to recover, although this fountain is only required if you were critically injured in the last fight.
You earlier saw a woman staring through the portcullis. Despite it being closed and having debris in front of it, that is the exit of the main hall. Enter the gap on the right side of the portcullis, and you will see the woman running away. You can chase her, but debris will cut you off and require you to enter the room on your right.
There is a sand cloud in this room, which you should absorb with the dagger. Continue to the back corner, and jump to reach the horizontal bar. Flip from bar to bar until you grab the ledge on the opposite wall, then shimmy to the right. Run along the wall past the two curtains. Wall run to the corner, and jump to the bar. The platform ahead leads to the room's exit.
You see another sighting of her in the next corridor, only for debris to block the passage. Simply head left to bar-jump across the pit. Drink at the fountain to heal, and enter the second room.
Run along the wall to grab the bar, and swing to the opposite corner. Around the corner, wall-run to the bars and descend to the floor. At ground level, you will be attacked by six enemies (with four in play at once). When combat is over, run to the corner near the bar with the torch. Run up the wall to jump to the bar. Use the bar to swing towards the same corner, and immediately use the wall to jump to the bar above. The ledge should be visible from the second bar, and you can climb into the hole to reach the next save point.