From OtherSpace: Encyclopedia Galactica
The Aegis is the 600 to 700 foot tall wall that surrounds the city-state of Fastheld. It was created in 0 BTA when Talus Kahar I offered amnesty and exile to any Shadow-Touched within the city-state in exchange for using their shadowed powers to erect a wall to protect the people of Fastheld from the Wildling threat.