The Chimaera is a modified Imperial I Star Destroyer, which served as Thrawn’s command ship throughout the course of his career dedicated to the Empire, from Commodore to Grand Admiral. Prior to the Liberation of Lothal, Thrawn used the Seventh Fleet to blockade the Outer Rim planet but was later defeated when Ezra Bridger (played by Eman Esfandi in “Ahsoka”) used the purrgils to drag Thrawn, the Chimaera, and himself into hyperspace. Since their departure in the “Star Wars Rebels” series finale, Thrawn’s return has been the subject of constant theory-crafting, along with that of Ezra’s fate, who was often theorized to have gone rogue (the actual reveal of his fate is much more endearing).
The ship’s most unique feature is the engraving of a chimaera on the underside of its hull, and Thrawn was struck by this specific inspiration during his time as Senior Captain of the Chiss Expansionary Defense Fleet. While standard Star Destroyers had double-barreled turrets, The Chimaera had eight-barreled ones, possibly tweaked to accommodate the Admiral’s grand ambition and his need for a foolproof airborne fortress that could tank enemies.
One of the ship’s earliest uses was during the height of the Galactic Empire when rebellion was just a spark in various corners of the galaxy. Thrawn was sent to squash these potential pockets of rebellion, which he proceeded to do over the years without any mercy, using the ship to turn the tide of some small-scale space battles, including the attack on the Lansend Twenty-Six space station to recapture Wookie slaves who had escaped with the aid of rebel groups. After winning this particular space battle, Thrawn went on to deal with various threats until the civil war started, weakening planetary defenses ruthlessly and apprehending malcontents who threatened the cause of the Empire.
Source From: www.slashfilm.com