Do a REVERSE and jump across to the stairs. Turn around and jump up to the ledge with the save game gem and save your game. Enter the THOR DOOR to your left. Inside is a cool plasma sphere shooting electric bolts to the floor. A pattern of blocks is laid out in a circular pattern. If you are in this circle when the bolts hit - you get zapped! Time the bolts and make your way across this room.
The next room has a large hammer suspended from the ceiling and some markings on the floor. Stand on the symbol. When you hear something break jump back and the hammer will smack the floor. Don't move! Wait for a couple of blocks to fall to the floor. Push the block a few times against the wall near the head part of Thor's hammer. Use it to climb up to the ledge where you can pull the second block out a few times then use it to climb and jump over to an even higher ledge.
Get the small medkit then jump across to the ledge on your left. Enter the small room and get the THOR KEY then jump back and climb down. Run through the electric room and make your way back and exit the THOR DOOR.
At the edge turn left and jump to a ledge that looks slightly different than the others. Your friend from earlier is shooting at you so hop to a small ledge on your right and kill the 2 bats that are attacking. Turn and jump to the middle ledge then go up the stairs to find a lever which opens the DAMOCLES DOOR. Climb the stair and enter the ATLAS DOOR.
Kill the gorilla waiting for you in here then run ahead and through the gate. A medkit is in the pit to your left. Run up the hill until a huge boulder comes rumbling towards you. Do a REVERSE and run away. As you near the pit do another REVERSE and drop back and grab the edge of
the pit. The boulder will sail harmlessly overhead. Start back up the hill and about half way jump to the ledge on your left. Jump up again and get the ATLAS KEY on the other side of the ledge. Make your way back and exit the ATLAS DOOR.
Go to the highest step and jump up and climb to the next level. Jump to the stairs on your left. Shoot some bats and go to the highest step. Jump to the middle ledge and go to the other side and enter the NEPTUNE DOOR. Go for a swim. The current will move you along but you need to swim up and to you left to enter a small tunnel. Pull the lever at the end of this tunnel then return to the main tunnel. Swim forward and get the NEPTUNE KEY. Go to the other side of the passage and surface quickly as you are probably almost out of air by now.
Climb out of the water and exit through the NEPTUNE DOOR. Jump to the middle ledge and climb down to the ledge across from the sandstone stairs. Jump over to the stairs and go down the the DAMOCLES DOOR. Get the medkit ontop of the door before you enter.
Don't worry about those swords hanging from the ceiling. Go to the next room and get the DAMOCLES KEY then hoist yourself up and get the shells and medkit on the ledge above. Leave this room slowly. The swords will start falling - just watch the shadows and listen for them to fall. If you walk you will be able to stop just short of the sword. Exit the DAMOCLES DOOR drop down onto the small ledge and once more to the ground where you can start shooting at the 2 cougars and that hostile explorer who's been after you. You can also save your game here (just in case).
The cougars will die and the explorer will run away again. Go to the door and use the 4 keys you've been collecting in each of the locks. The bars will be removed and you can EXIT this huge level. WHEW!