Ervyll is the king of Verden, one of the minor forces in the Northern Kingdoms. His son Kistrin was once a prospective suitor for Ciri, but she had other plans. Ervyll is married to Eliza, the sister of Freixenet, one of his governors.
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's fate afterwards is unknown.