The Keldon-class ships were a late 24th century fleet of Cardassian warships developed and built in secret by the Obsidian Order. The Obsidian Order was forbidden from having their own warships (or military equipment of any kind) and thus took great pains to keep the fleet hidden away from the oversight of Central Command. The Keldon class was a powerful upgrade to the Galor-class warships; the ships maintained the basic Galor layout, but improved mobility by adding rear fins. An expansion module added to the hull complemented the additional robustness of the ship design.
The ships were revealed to the Federation and Cardassian Central Command by the intervention of Maquis agents aboard the hijacked U.S.S. Defiant. Despite their cover being blown, the Obsidian Order continued building the Keldon-Class fleet in service of a joint venture with the Romulan Tal Shiar to team up and destroy the Founders’ homeworld in the Gamma Quadrant. The founders had been tipped off to the plan, however, and the Keldon-class fleet was obliterated in the ensuing battle with the Dominion.
As portrayed in Star Trek: Deep Space Nine - “Defiant” (TV, 1994)
The physical model seen as the Keldon-class ships are modifications of the model used for the Cardassian Galor-class ships. The alterations that transitioned the Galor-class into the Keldon-class were made by Tony Meininger of Brazil-Fabrication and Design. The changes were designed to be removable, so that add-ons could be removed and the models reverted back to use for the Galor-class. The Keldon add-ons were an extra set of fins placed on the aft end of the hull and an additional hull module latched on to the middle of the existing hull. The models were 3’ long. The Keldon-class model has not been used in filming since “The Die is Cast” and is one of the final ship models made that were not subsequently converted to a CGI version.