The Rom Knights were a militant group of Cardassian commandos that operated after the Dominion War. They were formed by Demos and consisted of rogues members of their government who believed that their leaders had sold out their future and as such also intended to get revenge for the deaths of countless Cardassians under the order of the Female Changeling.
Intelligence on the whereabouts of the Changeling was later received by Demos who led the group to assassinate the Founder leader of the Dominion who remained in incarceration at a secure Starfleet facility. This led to Demos staging a covert raid with the intention of assassinating the Changeling. However, the majority of the Knights were killed during the operation after one disaster after another came upon them. It was eventually discovered by Demos that Klyst had been sabotaging the groups efforts and had been working with Garak who wanted to stop any further retribution from being visited on Cardassia Prime. (DS9 comic: "Alien Spotlight: Cardassians")