Let's make this clear: The Chimaera is an Impstar I - one of the first ones, and one of the most prestigious, therefore its role at Endor. It was pretty high on the command hierarchy at Endor, although it had no Admiral on board, therefore Pellaeon's orders to retreat were obeyed. Somewhere during the Emperor's reign many of the ship's systems were updated to more modern Impstar II standards. It was among the ships that remained loyal to the Empire after Endor. Then Thrawn came, after Thrawn's death Pellaeon joins Clone Palpatine's Empire. During Operation Shadow Hand at Duro the Chimaera is heavily damaged, Pellaeon escapes, but most of his officers die. After Palpatine's death Pellaeon joins Teradoc he obtains the 13X. Then comes the events of Darksaber, and how Pellaeon obtained the Command of all Imperial Forces. Pellaeon has an SSD the Reaper as flagship, he orders intelligence to recover the Chimaera from Rebel hands, and he obtains a victory against Ackbar after he recovers the ship. Pellaeon then make a bold move and loses the Reaper and many Imperial ships, he returns to the Chimaera. The New Rep - Imperial treaty is signed there. He still uses it in the Dark Tide Duology, in Destiny's Way he has an SSD, and in REmnant he is back on the Chimaera.