Grand Admiral Thrawn was first introduced in Timothy Zahn's "Heir to the Empire" trilogy of novels. While those tales ended up being relegated to the non-canon Expanded Universe when Disney took charge of the Star Wars franchise, Dave Filoni later reintroduced the villain in Star Wars Rebels.
Since then, Zahn has panned more books (this time set in the current continuity) revealing Thrawn's past as a member of the Chiss Ascendancy and how he came to join the Empire.
He's been portrayed as an anti-hero of sorts, joining the Empire in order to protect both his people and the wider Galaxy posed by the threats which hail from the Unknown Regions. His time as an Imperial clearly sent Thrawn down a dark path, though, and Dave Filoni has made it clear he'll be a full-fledged villain in Ahsoka and the filmmaker's upcoming Star Wars movie.
"[He is definitely the bad guy in the New Republic era], in my eyes. When Timothy Zahn wrote Heir To The Empire, Thrawn became this very iconic villain, because he was different than anything we’d seen before," Filoni tells Empire (via StarWarsNews.net). "He wasn’t another helmet-wearing, lightsaber-wielding bad guy, you know? There’s a lot of pull to make characters that are like Vader, because it is so iconic."
"But the boldness that Tim had was to make somebody that wasn’t like that, that didn’t have those abilities, but could fight in a different way. In the words Star Wars, the ‘war’ part of it — him being a Grand Admiral, a leader, a military strategist, a Moriarty archetype, someone that will out-think you, out-strategise you — that really resonated."
"He’s a critical player in this time period," the filmmaker concluded. "We’re fortunate to have that character, and fortunate to have Lars [Mikkelsen] playing him."
It's going to be interesting to see how Thrawn is portrayed in the years ahead, particularly when the groundwork is clearly being laid for him to pick up where Emperor Palpatine left off as, well, the heir to the Empire. Ahsoka will set the stage for whatever he has planned, anyway, and we're sure Thrawn was up to no good during the years he was missing alongside Ezra Bridger.
What are you most excited to see from the Grand Admiral when he makes his live-action debut?