The intelligence chief was one of the organizers of the attack by the Scoia'tael on the mages' conference on Thanedd Island. Because the attack did not achieve its primary objective, de Rideaux and the emperor came to the conclusion that there were traitors among them, namely: Vilgefortz, Rience, Cahir, and possibly Isengrim Faoiltiarna.
The Nilfgaardian ambassador Shilard Fitz-Oesterlen and Letho talk about Vattier. The latter reveals to Geralt that he succeeded in obtaining information from Yennefer about the Lodge of Sorceresses. Apparently only Vattier, the Emperor Emhyr var Emreis and Letho know the plan to destabilize the Northern Kingdoms, murdering two of the Northern kings.