Sessile tree-dwellers from the obscure planet of Myrkr, the ysalamiri are among the most bizarre creatures of the galaxy. As part of a defensive mechanism that protects them from Force-sensitive pack animals called vornskrs, the ysalamiri have developed the unusual ability to "push back" the Force.
Ysalamiri are small, furry salamander-like creatures no larger than 50 centimeters long. Their long claws grow directly into the cores of the branches they inhabit, drawing nutrients from the mineral-rich trees. It takes special knowledge to successfully remove an ysalamiri from a branch without killing it.
A single ysalamiri creates a bubble in which the Force cannot be manipulated. In groups, the size of the bubble increases. Vast areas in which the Force cannot be used cover Myrkr.
Five years after the Battle of Endor, Grand Admiral Thrawn used ysalamiri in a cunning plan to topple the New Republic. Imperial engineers fashioned a special nutrient frame that allowed ysalamiri to be transported and kept alive once removed from the trees.
Thrawn used the ysalamiri in order to secure the allegiance of Dark Jedi Joruus C'baoth. With ysalamiri in place, Thrawn would have a distinct advantage over Force-sensitives like C'baoth, Luke Skywalker and Leia Organa Solo. Thrawn also discovered that strategically placed ysalamiri employed in Spaarti-based cloning chambers eliminated the clone madness caused by the disruption of identical Force patterns inherent in Spaarti clones. By using ysalamiri in his vast cloning facility in Mount Tantiss on Wayland, Thrawn was able to grow adult clones in a fraction of the recommended time.