In the mirror universe, the Eighth Happiness was a freighter under the command of Griffin.
In 2277, T'Prynn booked passage aboard the freighter and then convinced the captain to cut through the Taurus Reach to speed the voyage along. This shortcut was a violation of Imperial policy and the ISS Endeavour responded to this violation by stopping the freighter and boarding it. Griffin was interrogated by being flushed out the ship's airlock and then beamed back aboard the ship. Once the Endeavour was done, the Eighth Happiness was allowed to go on its way, but half the cargo was confiscated. T'Prynn later revealed that she had tampered with the ship's warp signature in order to draw the Endeavour's attention because she needed to talk to its captain. (Mirror Universe short story: "The Black Flag")