The Elasi were a group of humanoid pirates, who had settled in the Elasi Star Cluster. Their fleet was comprised mainly of ships that had been either captured or salvaged from scrap and rebuilt, but one of their primary ship configurations was made from components of old Klingon vessels that had been traded for dilithium. Most of these ships were nearly a hundred years old and on their last legs before they were traded, and the Klingons got the better end of the deal. Still, Elasi engineers were quite successful in converting several of the old ships into new pirate vessels and with the changes made, the ships had become fairly modernized.
the USS Enterprise (NCC-1701) fought this type of ship several times (Star Trek: 25th Anniversary). One of these ships was also stolen by a rouge orion, Seluk. He had a crew comprised of multiple alien races and they worked on many mercenary missions together (Star Trek: Eagle).