The Alliance

From Memory Alpha, the free Star Trek reference.

You may be looking for the Klingon-Cardassian Alliance of the Mirror Universe.

The Alliance was a group of ships led by the USS Voyager. During Voyager's flight home, it encountered an anomaly called "The Void", where all resources were virtually nonexistent, and piracy sustained everyone there. Captain Kathryn Janeway formed this alliance, which was based on the same principles as the Federation, though not all trapped species joined. By combining their efforts and technology to create a polaron modulator, and with some additional help from the natives of the Void, the Alliance succeeded in escaping. (VOY: "The Void")

The four ships that escaped The Void were the USS Voyager, a Hierarchy survey vessel, a Nygean ship and a ship of unknown affiliation. The fourth ship may have been the crew Janeway mentions who shared technology that tripled replicator efficiency.