Excalibur (free starship)

In the mirror universe, the free starship Excalibur was Galactic Commonwealth warbird in  service in the late 2370s. The ship had been built by the $𝜇$ and commissioned as IRW Valdore. Following the loss of its crew at the Battle of Bajor, the Valdore was recovered by Memory Omega and renamed Excalibur by Mac Calhoun, who became its new captain. 

Construction
In late 2378, the IRW Valdore participated in the decisive Battle of Bajor against the $𝜇$ and the $𝜇$. During the battle, the Valdore was heavily damaged and lost its entire crew. A microsecond before the Terran Rebellion  rammed a Klingon bird-of-prey to prevent it from launching a trilithium warhead at B'hava'el, the Excalibur's consciousness, $𝜇$, transferred its crew onto the free starship Enterprise and itself into the derelict Valdore.

Memory Omega recovered the hulk from the battlefield and transferred it to Erebus Station for repairs. When Director $𝜇$ led Captain Calhoun and $𝜇$ around the station to choose a new vessel, McHenry contacted Calhoun telepathically and reported the cloaking device was still in working order. Calhoun asked Saavik for the Valdore and had it renamed Excalibur.