Willemer also known as Vilmerius was an archpriest from Vizima and a sitting member of Foltest of Temeria's Royal Council. He did not like mages in the least. He was a provocateur during the witch hunts.
He was responsible for capturing, torturing, and the death of Philippa Eilhart during the witch hunts. Ironically, many years later, it was he who went down in history as a heretic and sectarian, while Philippa was remembered as one of the Martyr Saints.
- In The Witcher 3: Wild Hunt, there's a hospital in Novigrad called Vilmerius Hospital. It's not named after him however.