Back in April, ComicBook.com reported that Willem Dafoe was joining the cast of Justice League in an undisclosed role. While some assumed that Dafoe, who played Norman Osborn in the first set of Spider-Man movies, would play a villain, the report indicated that Dafoe would play a "good guy." Now we know that Dafoe will play Vulko, an Atlantean politician and longtime adviser to Aquaman.
So who is Vulko and what will his presence mean for Justice League? Originally, Vulko was introduced in 1967 as a political dissident and adviser to the former King of Atlantis, Trevis. When Aquaman was born with blonde hair (a deformity in Atlantean society) Vulko argued against casting the child out of the city, but he was overruled. Years later, Vulko met and befriended a grown up Aquaman in an Atlantean prison. When Aquaman escaped and became king of Atlantis, he appointed Vulko to act as his regent, allowing Vulko to make decisions on Aquaman's behalf when the hero was away from the city.
Although Vulko and Aquaman are usually allies, Vulko hasn't always been loyal to the hero. The elder Atlantean has abandoned Aquaman's side several times, usually when he feels that Aquaman is unfit to rule Atlantis. He also has a tendency to be at the center of Atlantis's political intrigue, and even became the King of Atlantis...albeit briefly. Unfortunately, Vulko was among the many citizens killed when the Spectre destroyed Atlantis during the events of Infinite Crisis.
DC reintroduced Vulko in the New 52 as an Atlantean living in exile. It was Vulko who explained to a young Aquaman about his Atlantean heritage. He later manipulated a war between Atlantis and the surface world in order to force Aquaman to retake the Atlantean throne from his half-brother Orm. Vulko's plan works, but Aquaman's first act as king is to imprison Vulko for his role in the deaths of hundreds of Atlanteans and humans. However, when Aquaman's ancestor the Dead King retook the throne of Atlantis, the two reconciled and worked together to defeat the ancient enemy.
If Vulko is appearing in Justice League, it probably means we'll at least get a hint of Atlantean politics and culture. Vulko's first priority is to his city, and that means that he could be opposed to his king wanting to sign up for a superhero team made up of surface dwellers. This is almost certainly setup for the Aquaman film, as well, one of the first two premiering after the big team-up movie. We'll have to wait another year or so to find out just what sort of role Vulko will play in the movie.
Justice League comes out November 17, 2017.