For a quick complete, if you are able to use fly spells, drop into the water and head east. Fly up to the platform where you see a squared tan stone structure, and head down the passage to the south. Pull the chain to open the first part of the giant portcullis guarding the exit.
Go back in the water, head west and take the teleport you find to go to a small fort in the middle of the map. Upstairs in the fort, you will find the second pull chain to activate.
Now, drop into the moat and take the teleport there to reach a room with several "cupboards" containing potions. From the potion room, head through an illusionary wall up the stairs to find the pentagram. Teleport back to the moat and head through the now open passageway to the exit.
