Calypso (ISS Enterprise-D)

In the mirror universe, the Calypso was a Terran Empire auxiliary vessel, a captain's yacht in Imperial Starfleet service in the 24th century. In the 2360s decade, the Calypso was assigned to the dreadnought. 

History and specifications
Following an investigation into the Empire's narrow supply lines and the interrogation of a Bolian supplier aboard the Enterprise, Captain $𝜇$ loaned his enforcer Commander $𝜇$ the Calypso for further investigation. The Calypso left the Enterprise and successfully evaded a trio of Klingon-Cardassian Alliance birds-of-prey at the edge of the Sol system. 

The Calypso traveled to Imperial Alpha, where Data checked the records of $𝜇$, former Emperor of the Terran Empire. 

The information he gained led Data to Spock's secret hideout in a jungle on a planet. Data dispatched the Tellarite mercenaries and confronted Spock. 

Armed with the knowledge of parallel universes gained from conversing with Spock, Data had a means to open new supply lines for the Empire. The commander killed the former emperor and his guards, boarded Calypso and sailed away. 

Data returned the information to Captain Picard, and the ISS Enterprise embarked on a series of raids in the primary universe, beginning at Naia VII and with the infiltration of the USS Enterprise (NCC-1701-D).