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King Ervyll was a ruler of Verden, a minor realm amongst the Northern Kingdoms. His son, Prince 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 second Nilfgaardian War, Ervyll betrayed his Northern allies, swearing fealty to Nilfgaard. His son opposed this move, and started a guerilla uprising that sought to depose his father and remove Nilfgaard's influence on the kingdom. Eventually, they were successful, and Prince Kistrin drove his father out, seizing the throne. Ervyll's fate afterwards is unknown.