Star Wars Rebels season 3 got its own panel at the 2016 Star Wars Celebration in Europe. There, Rebels show-runner Dave Filoni and cast members Tiya Sircar (who voices Sabine Wren) and Sam Witwer (who voices Darth Maul and Emperor Palpatine) presented a couple of fresh clips from season 3 to the crowd, in addition to a full-length trailer for the season that's on the horizon.
The Rebels season 3 trailer revealed several intriguing tidbits about the episodes that lie ahead. However, the most exciting reveal in the footage was that of season 3's main antagonist: beloved Star Wars Expanded Universe (now Star Wars Legends) villain, Grand Admiral Thrawn. In addition, Thrawn's creator, Timothy Zahn, is confirmed to be writing a new canon novel featuring the character that will be published in 2017.
Zahn appeared during the Rebels panel at Star Wars Celebration by way of a pre-recorded video message, saying it was an "incredible honor" for him to work with Filoni and the rest of the Rebels crew to adapt Thrawn for the animated TV show. You can check out the official cover artwork for Zahn's upcoming Star Wars: Thrawn book, below:
Thrawn, a blue-skinned alien (who belongs to the race known as the Chiss) and tactical genius who serves the Galactic Empire, was introduced in Zahn's Heir to the Empire book trilogy (set five years after the events of Star Wars: Episode VI - Return of the Jedi). The character took command of the Empire's forces following the death of Emperor Palpatine in the Star Wars Legends continuity, but will presumably serve a different role in the newly-established Star Wars canon. Thrawn's addition to the Star Wars Rebels ensemble in season 3 has been rumored for some time now, based on the idea that "this time he will be using his evil brand of genius against the the heroes of the starship Ghost."
Here is what Filoni had to offer the crowd at Star Wars Celebration, with regard to Thrawn's legacy as part of the Star Wars EU (prior to Disney's acquisition of Lucasfilm in 2012):
“You couldn’t have grown up a Star Wars fan without encountering Thrawn in Heir to the Empire. It was a dark time when there weren’t any more movies, and it blew our minds that there could be more.”
Grand Admiral Thrawn will be voiced on Star Wars Rebels by Lars Mikkelsen (House of Cards), the older brother of Rogue One: A Star Wars Story costar Mads Mikkelsen. You can check out screenshots of Thrawn from the upcoming Rebels season 3 below. That includes an image of Thrawn alongside the Planetary Governor of Lothal, Arihnda Pryce, who's also making her Rebels debut in season 3 (after only being mentioned by name during the seasons past).
Star Wars Rebels season 3 premieres on Disney XD in fall 2016. Star Wars: Thrawn will be published in 2017.