From the Ashk Setting Guide
The Empire stretches from Ashk in the West to the Endless sea to the East, and is comprised of more than a dozen full nations, as well as many smaller regions.
When the Empire conquers a nation those who have been conquered are given the option to become full Aparthian citizens, which grants them voting rights, as well as a stipend from the government after five years of citizenship.
To become an Aparthian citizen, one must renounce their existing religion and convert to the worship of Sofos the Grandfather [NG] . A citizen must also swear fealty to the Empire and promise to protect its borders through possible conscription.