There are two paths through Fort Cruth. The bottom path has better loot but more enemies, and the top path has barely any loot but takes you to the boss fight almost immediately.
There are two Arrows on the ground in this area, as well as two Kobolds and three Ax Gnolls. In the next area there is a Hammer and another Ax Gnoll, and in the chest you'll find 10 SP and a Lightning Bolt ring. Continue to the right to fight the Displacer Beast.
In this first area are two Ax Gnolls and a Dagger. Break the table for a Hammer. The chest contains a book and 62 SP. Push the suit of armor to the left and enter the secret area.
In the secret area you'll fight eight Kobolds. The top chest (trapped with Fire) and contains a healing potion and 70 SP. The bottom chest contains 10 SP, a Hammer and a Dagger (replaced with Magic Missile if an Elf, or Continual Light if a Cleric). Leave the secret area.
In the next area you'll fight nine Skeletons. There is a Dagger on the ground, and the chest contains 111 SP and a Fire Ball ring. After the battle head to the right and hit the switch, being careful not to walk too close to the door or you'll go through it. Now head back and push the suit of armor to the left.
In this room there is a white button to the top right. You can hit this with any projectile (including a Magic Missile ring or spell). In the room beyond this you'll find a chest (trapped with Dead Fall) contains a Cure Serious Wounds ring, Boots of Speed, and 100 SP. Leave this room and go up the stairs to fight the Displacer Beast.
As the soldier indicates, there is only one shadow. The other is an illusion cast by the Displacer Beast.