The corvette.
A CR90 corvette played a role during the Defense of Ralltiir. Captain Bren Derlin was in command of the vessel at the time.
Based on intel from Tycho Celchu, an Imperial TIE pilot who defected to the Alliance, it was sent to Ralltiir to assist in getting Ralltiir scientists who wanted to join the Rebel Alliance off the planet. However, as the battle progressed, stormtroopers boarded the ship, leading to a major gunfight between the Rebels and the Imperials before the ship was cleared for departure.