This walkthrough is meant as a general guide only. It may not include every pickup or secret. There may also be alternative ways of approaching situations within the game.
The level starts with a cutscene of the outside of a pyramid and Lara sliding backwards down a slope. Before the cutscene ends, hold the ctrl key as Lara begins to slide to grab the edge of the slope. Shimmy to the left hand corner and let go. Slide until you see the camera angle change, then take a jump and grab the climbable wall over the flame. Drop to land in the lefthand corner (you will not catch on fire). Turn left to face the slope and begin sliding. Before reaching the end, jump and curve right to avoid the boulder. Face south and sidestep to the middle of the ledge. Take a standing jump over the gap and the double doors open. Arm weapons and shoot the scorpion. Pickup the Shotgun. Jump back and grab the edge of the ledge and drop down into the water below. Dive down and pickup the Lasersight and climb into the crawlspace. Crawl through the water and climb the block at the end. Head forward and drop into the water through a hole in the floor. Swim to the middle of the west wall and climb out of the water. Head up the hill to the right of the blue light into a well concealed alcove. Climb the block, turn around and jump up and grab the ledge above. Pull up into the corridor and run to the end, into the next area.
Turn left and head down the stairs. Use the series of blocks along the wall and jump your way to the back of the room (east wall). Angle left and take a running jump to the ledge. Pickup the flares and drop down. Enter the alcove in the north wall and drop into the hole in the floor. Push the floor lever and arm weapons. Shoot the 2 scorpions and climb out. Shoot the 4 scorpions and head forward into an entrance in the south wall. Enter the alcove in the south wall and drop into the hole in the floor. Push the floor lever and a "secret" sound chimes. Arm weapons, shoot the 2 scorpions and climb out. Head to the west wall. Jump up and grab the edge of the ledge and pull up. Angle left and take a running jump to the first block. Take a standing jump to the second block and safety drop down. Head to the south/west corner and climb the first "claw" of the scorpion statue. Pickup the large medipack, turn north, drop down and climb the second "claw". Pickup the large medipack, face south, drop down and into the hole in the floor.
Descend the staircase and push the floor lever at the bottom. Immediately reverse roll, turn right and up the stairs until you reach the flares. Reverse roll and take a running jump and grab the ledge above. Pull up to avoid the boulder and safety drop back down. [tip: Alternate route (but probably not the intended): After pushing the floor lever, head forward (south) into the alcove to avoid the boulder. Turn around and take a standing jump into the north/west corner. Take two side jumps to the right to clear the boulder and head back up the staircase. Pickup the small medipack and flares. At the top of the staircase, angle right and take a running jump across to the north/east ledge. Crawl through the crawlspace and take a running jump west to the middle structure across the chasm. Turn left and enter the corridor. Follow the right wall to an alcove with an ankh symbol on the floor. Climb the wall, pull up and arm weapons. Shoot the 2 scorpions and crawl to the right. Follow the corridor left until you reach the ledge. Turn around, jump back and grab the edge and shimmy right. At the end, pull up into another crawlspace. Follow the left wall until you reach a hole in the floor. Lower into the pit and shimmy right. Note: Some players encountered spikes in this pit, but I didn't. Pull up and crawl until you can stand. Turn left and head to the north/east corner. Facing east, jump up and grab the monkey swing on the ceiling and swing to the alcove across the chasm.
At the end, let go and immediately grab the edge of the crawlspace and pull up. Crawl through, turn around and lower into the next room. Reverse roll, arm weapons and shoot the vase ahead and the door behind opens. Head through the newly opened door and take a running jump to the sarcophagus. Jump up and grab the monkey swing above and swing over to the other side. Reverse roll, drop to the lower block and pickup the Eye Piece #1. Step forward to the end of the sarcophagus and jump up and grab the monkey swing above. Swing to the other side as a mummy materializes in the room ahead. Drop down and climb the ladder at the end of the room. At the top, let go and quickly grab the edge of the crawlspace. Quickly pull up before Lara positions her feet back onto the ladder. Crawl through, reverse and lower out of the crawlspace. Let go. slide down a small ramp and grab the edge. Climb down the ladder back into the Main Atrium.
Turn right, head to the end wall and turn right. Head into the shallow water and follow the right wall until you reach a corridor with a large statue (Screenshot 1). Pull the statue as far as you can and turn around. Follow the left wall back out of the water and around the entire central structure until you reach the other side of the statue. Push the statue to the end and the gate on the left opens (Screenshot 2). Pull the statue one space back to access the opening and head back around to the other side. Face the opening and jump up and grab the edge and shimmy to the left hand side. Pull up and you will not catch on fire in this corner of the block. (Screenshot 3) Turn left to face the wall and take a side jump right over the fire. Immediately run forward into water and surface for air.
Face north, dive into the water and turn right. Swim forward to the east wall and turn right again. Follow the right wall and swim until you reach a sloped corridor in the north wall. Swim through the corridor and surface at the end. Pull up, climb the stairs, enter the tomb and pickup Eye Piece #2. Immediately exit the tomb as another angry mummy materializes behind you.
Secret #1: Drop into the water, swim through the corridor and turn right. Swim to the wall and turn left. Follow the left wall all the way around into Secret #1. Pickup the Crossbow Ammo. Reverse roll, swim forward and follow the right wall all the way back until you reach the sloped corridor in the middle of the north wall. Surface for air.
Drop into the water, swim through the corridor and turn right. Swim to the wall and turn left. Follow the right wall all the way around until you reach an underwater room at the end. Swim up through an opening in the ceiling and reverse roll. Swim west through the corridor and surface. Pull up, head through the newly opened gate and climb the block back into the Main Atrium.
Turn left and make a hairpin turn left around the rust coloured column into the water. Facing east, head towards the ramp near the large statue. Step onto the first ankh symbol (screenshot) at the bottom of the ramp and watch a cutscene as the opens door at the top. Head up the ramp, avoiding the mummy and enter through the newly opened door. Arm weapons and shoot the scorpion inside. Combine the two Eye Pieces and place the Eye of Horus into the wall receptacle. Pass through the door and the level ends.
[Note: The following secret is included at the end as I could not find a way to obtain it other than to use DOZY. Although there is a textured wall in the corner that may have been meant to be a ladder, in the level was not climbable.]
Secret #2: Head to the south/east corner of the Main Atrium. Type DOZY and float Lara to the top of the ceiling where there is a ledge. Drop to the ledge using the SHIFT key and the secret sound chimes. Crawl into the crawlspace until you can stand up. Arm weapons and shoot the 3 scorpions that materialize. Pickup the Crossbow.