Now comes PHASE FOUR, a test of agility—and if you're playing the co-op game, teamwork. There are no enemies, just a shifting pattern of ice vents. The vents in the upper right corner come on and then begin to activate counterclockwise around the room. They don't move especially quickly, so as long as you stay alert, it's not to hard to keep ahead of them.

Here Lara happens to be standing in the lower right corner when the vents come on, so she's in no danger yet, since it will take a while for the active vents to work their way around the room toward her.

As the active ice vents approach, use the Staff of Osiris to rotate the huge gears so you can jump across to the other side of the room where it's safe.

This is also a good opportunity to pick up more health and ammo, since you'll cover the entire perimeter of the room while avoiding the vents.

Continue running counterclockwise around the room, jumping past the gears when you come to them...

...and staying ahead of the active vents.

After the vents have made a full counterclockwise circle and then reached the upper corner once more, they will reverse direction and start moving clockwise.

It will look as if you're about to be boxed into the right corner, but don't panic. Keep the staff raised and wait for the vents below and to the left of the huge gear to clear.

You should have just enough time to jump across before the vents beneath you activate.

[Part 3 | Part 5 | Return to the Tomb of the Pharaoh Walkthrough]