The Wanderers were a mysterious group of hundreds of thousands of creatures belonging to all the sentient humanoid species that inhabited Realmspace. They inhabited the inner surface of the crystal sphere, their hands all bearing the mark of Torm.
It was said that the Wanderers were the souls of extremely evil individuals that had died within Realmspace. About once every five years, one sufficiently evil person would be selected upon death to join the ranks of the Wanderers, doomed to walk the sphere and perform its silent chant forever.
The group continuously marched side by side on the sphere in a north-south direction, with no need to breathe, silently moving their mouths and hands as if casting spells.
Their placement on the crystal shell was the reason portals in and out of the sphere were possible. They were not indestructible, however, and if they were to be wiped out, no portal would open until another evil creature died within the sphere. 
During the Time of Troubles, the chanting of the Wanderers had temporarily ceased due to the fall of Realmspace's powers. For the duration of this period, no portals could be opened through the crystal sphere.