Grand Admiral Thrawn has replaced Palpatine in Star Wars as the shadowy force who feels like he could behind almost everything in the early years of the New Republic. While it's Star Wars Rebels that placed the fan-favorite Chiss mastermind back in canon, it's The Mandalorian's Season 2 that reminded fans why he's still a force to be reckoned with. But Thrawn's original introduction wasn't without a few hurdles, as 1991's Heir to the Empire also introduced his controversial "pets," the ysalamiri.
Timothy Zahn's original Thrawn Trilogy, beginning with Heir to the Empire, became the biggest piece of groundwork for almost three decades worth of now out-of-canon Legends material. With Thrawn as the villainous but honorable mastermind behind several intertwining plots, the Grand Admiral knew he would need some extra tools to survive a concentrated assault from the New Republic and its fledgling new Jedi. His answer was the ysalamiri, force-repellent lizards harvested from the planet Myrkr. Already in use to stabilize his rapid clone program, his mercenary ally, Talon Karrde, found a way to make the fragile lizards portable, extending their anti-Force effect.
On the surface, the lizards aren't too much of an issue. They're prey animals that developed a method to survive on a world where their dominant predator, the dog-like vornskr, uses the Force to help track their prey. But the Star Wars fandom found problems with the ysalamiri quickly. The first printings of Heir to the Empire made the ysalamiri's Force-nullifying powers act in direct counter to canon, describing the creatures as being able to displace the Force. Fans rushed to point out that a lifeforce present in all living beings couldn't be pushed out as the book first described.
The rest of Zahn's trilogy, Dark Force Rising and The Last Command, took steps to clarify how the ysalamiri actually worked in reference to Force-canon by suppressing or dulling the ability to detect or use the Force in a bubble-like radius around the lizard. The 2011 reprint of Heir to the Empire also updates its descriptions of a ysalamir's ability to match. But that's not the only problem the creatures caused the Legends universe.
Like Superman's vulnerability to Kryptonite, the ysalamiri are a clever method of giving a villain a chance to match their heroic nemesis on equal footing. And like Kryptonite, the ysalamiri quickly started to feel like they were popping up nearly everywhere in the Star Wars Expanded Universe. From gaming rulebooks like the Wizards of the Coast 2000-2009 tabletop Star Wars RPG to future novel entries in the EU, the ysalamiri and their new portability became a hard counter to the Jedi. Ironically for Thrawn, his brilliant strategic move that upended the battle against the Jedi became a brainlessly reliable tactic from then on.
The announcement of Thrawn's return in Star Wars Rebels delighted fans at a 2016 Star Wars Celebration event, but there were some rumbles of concern that the ysalamiri would also come back. A Facebook post from the official Star Wars Rebels account quickly clarified that, although the show would homage Thrawn's infamous lizards, the ysalamiri wouldn't become part of canon again. And a now-deleted tweet from creative executive Pablo Hidalgo also underlined that decision, and it's not likely that Thrawn's return in the upcoming Ahsoka will renege on that.
Produced by Dave Filoni and Jon Favreau, Ahsoka stars Rosario Dawson and will stream on Disney+. The series does not yet have a release date.