The small, fast Vulcan ship Spock flew in 2387 carrying red matter to stop the Romulan supernova, later stolen by Nero in the Kelvin timeline.
The Jellyfish is a small, fast Vulcan ship built to carry a large store of red matter. Ambassador Spock piloted it in 2387 in an attempt to stop the supernova threatening Romulus by creating a black hole to absorb the explosion. He arrived too late to save the planet, and both his ship and the Romulan mining vessel Narada were drawn into the black hole and sent back through time.
In the new timeline created by the Narada's arrival, Nero captured Spock and the Jellyfish and used a portion of the red matter to destroy Vulcan. James T. Kirk and the younger Spock later took the ship back from the Narada. The young Spock flew it into the Romulan vessel, and the remaining red matter created a black hole that destroyed the Narada as the Enterprise escaped.
The Jellyfish is central to the 2009 film Star Trek and links the prime timeline to the Kelvin timeline. Its design hints at future Vulcan technology, and its cargo of red matter became one of the most powerful substances in the franchise.