When you first enter this level make your way to the northwest corner and go into the room there. There's a control panel to the south of the room which you can use to gain access to the southeastern quarter of the map if you have enough Vahnatai Lore. I don't know exactly how much you need, but I did it with a total of 11 Vahnatai Lore in a Singleton game.
Now make your way to the southwest corner of the map, stopping in the room with the four beams forming a + sign to pick up a Shard of Release.
Make your way to the southeast corner. Go through the doorway which should now be open and then south again until you reach an area completely blocked with boulders. Use Move Mountains Lv.3 on the Mossy Boulders to reach a body with a few items including a Crystal Imbued Shield.
Go further along the southern wall until you see a cracked section of wall. Use Move Mountains here to gain access to two Mind Crystals. Remember not to use the Energy Pulse Mind Crystal, but pick up the Resistance Mind Crystal.
Continue along the passage, west, then a little north then east until you see some Vahnatai Undead. Kill the Undead then check the four rooms to the north to pick up a few different crystals.
Continue along the passage until you're in the northeastern section of the map.
Make your way back towards the west, stopping to kill the Vahnatai in the guard room. One of them has a key that unlocks some of the doors on this level.
Check the rooms off the guard room to find a few more rooms containing some potions and other items, then head out the eastern exit.