He is painted as possibly a pedophile as well as a racist. He had designs on Brokilon and hated Eithné (as she did him) and even offered a reward for dryad scalps.
During the 2nd Nilfgaard War, Ervyll betrayed his allies in the North, swearing fealty to Nilfgaard. His son, Prince Kistrin, opposed this move, and started a guerilla uprising, aiming to depose his father and remove the Nilfgaardian influence from the kingdom. Eventually, they were successful, and Kistrin drove his father out, seizing the throne. Ervyll is then assassinated soon after.