-- note -- this was copy and pasted from the wookiepedia fandom
During his campaign against the New Republic, the Chiss Grand Admiral Mitth'raw'nuruodo sent a single Spaarti cloning cylinder to his facility on Nirauan to create a clone of himself. Intended as a fail-safe in the case of Thrawn's death, the clone remained in his cylinder beneath the facility for almost ten years. But in 19 ABY, the clone was discovered by Jedi Master Luke Skywalker and the former Emperor's Hand Mara Jade, and the clone was destroyed when the cylinder's generator was overloaded in a fight with the facility's defenders.