Tracking Down Yennefer
Vilgefortz tracked Yennefer of Vengerberg to Nazair as he was in need of her help. Nilfgaard had been conscripting mages into their service. And since neither of them possessed a letter of safe conduct, they both needed to leave as fast as possible. He needed Yennefer to accompany him back to Aretuza. He and Tissaia needed her help. Tissaia even said herself that Yennefer was the best student she'd ever taught.
Vilgefortz brought Yennefer back to Aretuza with him, where he and Vanielle of Brugge informed her that Nilfgaard was planning to attack Cintra. Not that Yennefer cared. She only cared for finding Tissaia. To her surprise, Tissaia had no idea Yennefer was in Aretuza. Vilgefortz lied to Yennefer in hopes of convincing her to join their cause.
Vilgefortz was one of many mages who attended the conclave of Northern mages in Aretuza. Artorius, Stregobor, and Tissaia led the conclave. Artorius and Stregobor had no desire to go to war with Nilfgaard, especially not on behalf of Cintra, who had rejected their mages for decades. However, Vilgefortz worried that more kingdoms would fall after Cintra as Nilfgaard wanted the entire Continent. Rather than watching them fall, Tissaia wanted to help Cintra defeat Nilfgaard. Vilgefortz, Sabrina, and Vanielle sided with Tissaia, wanting to convince the kings to send their armies and arguing that if they didn't stop Nilfgaard now, more kingdoms would fall.
Fringilla arrived at the conclave and denounced any suspicion that Nilfgaard was planning to take over the Continent. She stated that under their new leader, Emperor Emhyr, Nilfgaard had strengthened trade and funded research. Tissaia accused Fringilla of rejecting the order and way of life that took centuries to build. Fringilla retorted that they had simply modified it, and had taken a new path, guided by the White Flame. She claimed that Nilfgaard believed in shared sacrifice, and that there was no such thing as dark or light magic. Fringilla argued that in taking Cintra, they had a chance of saving the Continent. The mages put it to a vote. Unfortunately, most sided with Stregobor and Artorius in allowing Cintra to fend for themselves.
Battle of Sodden Hill
Approximately 60 mages, Vilgefortz, Triss, Yennefer, Tissaia, Vanielle, Coral, and Sabrina included, board a ship headed for Sodden Hill. They must get to the Elven keep that guarded it before Nilfgaard did. They had already sent word to the Northern kingdoms. Temeria and Kaedwen agreed to join them in defending the land. The plan was to protect the keep. Once on land, Yennefer questioned Nilfgaard's strategy of sacking Cintra and exposing themselves. Vilgefortz explained that the bigger picture was often left for history. Their task was much clearer: hold Sodden and save the continent.
Vilgefortz, Triss, Yennefer, Tissaia, Vanielle, Coral, and Sabrina arrived at the keep, the only thing separating Nilfgaard from the North. They were greeted by a man. Yennefer advised him to take the children and hide, but as he explained, there was no more hiding from Nilfgaard. Their only chance was to fight.
The keep was attacked by Fringilla and Nilfgaard in the late hours of the night. The sun had risen and the Northern mages made it through the night. Unfortunately, Nilfgaard arrived much sooner than they anticipated and the Northern armies were still a ways out. There were only 22 of them left, Vilgefortz, Triss, Yennefer, Tissaia, Vanielle, Coral, Atlan Kerk, and Sabrina included. They witnessed as a thick fog consumed the mountains around them, signaling Nilfgaard's encroachment.
On Yennefer's command, Vilgefortz portalled to Cahir's destination, taking out half a dozen soldiers before getting to Cahir. During the fight, Vilgefortz was disarmed multiple times, each time using magic to return his sword, despite Yennefer's warnings to reserve his chaos. Vilgefortz was eventually bested by Cahir and with his chaos depleted, Cahir kicked him off the hill. Vilgefortz rolled down the hill and hit his head on a tree stump. Vilgefortz, once awakened, found dozens of dead Nilfgaardians in the woods and a wounded comrade. Instead of saving him, Vilgefortz bashed his head in with a mace.