Vanja is an Undead Vampire Spawn who is imprisoned in Cazador's Dungeon. He is one of the children recently kidnapped from the Gur by Astarion and forcibly turned into a vampire spawn.
As the party progresses through Cazador's Dungeon, they inevitably pass by a prison containing various children Vampire spawns, including Chessa. Like Chessa, Vanja can either be consumed or set free depending on the choices made after slaying Cazador.