At the start of the map, go straight ahead to the docks. Turn right and follow the stairs on the edge of the area to the yellow key room (1). Press the switch to lower the key and collect it. Return to the starting area and turn right. Pass through the yellow door and go straight ahead. Go through the wooden door at the bottom of the stairs and turn right again. The rooms on either side of this hall contain some extra wand crystals and crystal vials that you may want to collect (2). Go to the end of the hall to a room with a window. To the right is a stairway up. Head up this stairway and press the switch on the wall to open the sealed door that you passed earlier (3). Drop down and go through the door. Down the hall and to the left, you will find a depression. Step into it and the stairs will rise. Go up the stairs, turn right, and head to the exit (4).
In the southeast corner of the starting room, go behind the barrels and press on the brighter wall. You will find a chamber with a Silver Shield.
Immediately after opening the first wooden door, you will see a wall with a demonic face that has a mouthful of skulls. This is a secret door. Open it to collect Gauntlets of the Necromancer and a pair of wand crystals.
When you come to the room with the window, check the north wall for a panel with an eagle insignia. This is another secret door. Pass through it to reach a platform near the docks where you can collect a Tome of Power. Do not drop down to the water, but instead pass the corridor you arrived from and follow the next to find an Ethereal Crossbow. You can also reach these passages by a second secret door that looks just like the first and is located in the corridor above the window room. The actual secret tag is at the top of the stairway from this second door.
After pulling the switch that opens the sealed door, backtrack to the window room. You will find that a teleporter has opened that leads to the water outside, where you will find a Bag of Holding.