The Borg Queen's ship was a diamond-shaped vessel used by the Queen in 2375, which pursued the Delta Flyer into a transwarp conduit and was destroyed when Voyager collapsed it.
The ship appears in the Voyager feature-length episode Dark Frontier. The Queen lures Seven of Nine back to the Collective by threatening Voyager, and Seven is brought to the Unicomplex, where the Queen tries to make use of her knowledge of humanity for a planned assimilation of Earth.
Janeway follows in the Delta Flyer, fitted with a stolen transwarp coil and shielding devised years earlier by Seven's parents, the Hansens. She recovers Seven from the Queen's chamber and flees into a transwarp conduit with the diamond-shaped ship close behind.
Voyager is waiting at the far end. As the Flyer emerges, the crew fire torpedoes into the conduit's mouth, and the pursuing vessel is torn apart as the passage collapses.