Ysalamiri were creatures that resembled lizards and possessed four eyes. During the Galactic Empire's reign, Grand Admiral Thrawn of the Empire had two sculptures of ysalamiri. These sculptures, crafted from green, brown, and yellow materials, were located in his office on the Chimaera, specifically positioned behind his desk.
The sculptures of ysalamiri were first seen in Star Wars canon in the 2017 Star Wars Rebels episode titled "Through Imperial Eyes," which was the seventeenth episode of the show's third season. The name of the creature was revealed in the Behind-the-Scenes Gallery of the episode guide for "Through Imperial Eyes" on StarWars.com. They initially appeared in the Star Wars Legends continuity in the 1991 novel Heir to the Empire written by Timothy Zahn. In Legends, the plural form of the creature's name was ysalamiri, while the singular form was ysalamir. Zahn stated that the concept of a creature capable of hindering a Jedi's connection to The Force was the initial idea he conceived for the story after his agent informed him about the opportunity to write a book series continuing the Star Wars narrative after Star Wars: Episode VI Return of the Jedi.
In Heir to the Empire, ysalamiri were described as furry lizard-like beings native to the planet Myrkr. They possessed the ability to disrupt a Jedi's access to the Force. Thrawn utilized them to control the powers of his unstable ally, the deranged Dark Jedi Joruus C'baoth. Thrawn later deployed them against his foe Luke Skywalker in subsequent installments of The Thrawn Trilogy. Ysalamiri subsequently appeared in various other Legends works, including Zahn's Vision of the Future.
Zahn initially faced numerous complaints from readers regarding Thrawn's explanation in Heir to the Empire that ysalamiri could "push back" the Force, arguing that the Force, originating from all living beings, could not be "pushed back" in that manner. He later clarified that Thrawn's explanation was inaccurate, stating that ysalamiri simply suppressed the level of the Force present, a distinction that was subsequently illustrated more clearly.