Once you leave the starting city (Tangramayne). You will find Fanskar's Fortress at N27 E17 in the Wilderness.
To enter, you need the master key which is obtained in the Tombs in Ephesus city.
Ephesus is located at N40 E15 in the Wilderness.
The Tomb is located at N7 E8 in Ephesus.
There is an old man located at N10 E8 in level 2 of the Tomb that will sell the key for 50,000 gold.