Entrance HallFollow the passage. You'll come to a chamber with four passages. The one to your left has a couple of closed gates. The one ahead will be used later, and from the other side. (To avoid some trouble at the end of the level run towards the passage ahead. Turn around and jump backwards till you hear the rumbling of a boulder. Run out of the passage and jump to the site.) On the right is a lever at the wall. This will open the passage on the right. Two raptors will come out of this passage. Shoot them. Then enter the passage. There you'll find a save crystal. Don't use it yet.
Passage on the Rightlever on the other side. This will open one gate in the left passage in the entrance hall. Jump back over the spike pit. Return to the spot with the save crystal.
Passage in the Middle(Now to your right.) Run towards an alcove with a lever. The floor will break underneath your feet. You will drop down into a cave where you will be attacked by three wolves. Shoot them. Then run up the ramp. Pull out the dark brown movable crate. Then get to one side of it and push it out of the way. Enter the next passage. Run up the stairs. Stop at the pit. Drop down and pick up the small medipack. Climb further up. Pick up another medipack, then use the lever to open a second gate in the left passage in the entrance hall. Drop down into the pit to end up at the beginning of the passage you entered. Return to the spot with the save crystal. I recommend using it now.
Passage on the LeftOne path leads towards another red block (2) and one in the other direction leads back towards the chamber with the unused lever. Be sure to hear the noise of an opening door between the lever-chamber and here, otherwise you have to go there and make sure the path is opened up. If you wonder what you have achieved: You have opened the secret passage! lever at the end. This will change the position of the first red block. Get back outside. Now get towards the lever you still haven't used and use it. Follow the "secret" passage. Step out at the end. Make a running jump onto the red block. Turn slightly to the left and make a running jump towards the other red block. Turn right and running jump into the entrance. Use the lever to open the last of the three gates. Make a running jump to get out of the passage and to cross the spikes. Climb back up into the passage where you first entered and return all the way back to the entrance hall, take the unmarked passage. On your way, you have to kill another Raptor.
The ScionNow enter the passage opposite, which is now open. Use the save crystal. Run towards the stairs but mind the darts.
The Velociraptor is very dangerous. You should pick a good weapon against him, or try to get out of his range. In the area where you meet the raptors first you can find the shotgun. This might prove helpful, but you will also need it against another opponent. Try to shoot raptors from above, while standing on a rock, or keep moving. Try not to get caught in a tight corner.
To read more on bats, please visit WikiRaider.