In Curse Of Strahd, six Vampire Spawn were released in his town and murdered many innocents. This coincided with a sudden appearance of Strahd himself in the Vallaki Town Square, flying atop the flaming Nightmare Beucephalus. Baron Vargas began to grow increasingly more unstable after this, he met with The Pack, the group of adventurers responsible for dispatching the vampires. He requested that they investigate Fiona who he believed was responsible for the disaster, and purchased an expensive necklace from them to fund their activities.
The attack rattled Vargas' unshakeable belief in his rule, as he believed he had failed his family's legacy. He retreated inward, never leaving his mansion, and employed half the town's guard to patrol his mansion. This left room for tensions to rise in Vallaki, and for the first time, crimes began being committed without fear of reprisal. The populace's trust in the Burgomaster was at an all-time low, and Fiona secretly stoked greater sentiment against him.
To maintain loyalty, he forced the townsfolk to attend another festival, where he would re-establish "hope". This lead to the Riots of the Blazing Sun, where he attempted to have Gadof Blinsky hanged for laughing at him, and he was chased down by the angry mob. Alongside Viktor, he was speared into a wicker sun, hoisted, and then burned alive.