The Obsidian Order got destroyed and dismantled following the joint attack with the Romulan Tal Shiar on the founders home world in the Gamma Quadrant. The predicted death count of Obsidian Order agents was 95%, this along with Tain's (Obsidian Order Chief) dissapearance led the Order to Crumble. However it is suspected that the Obsidian Order has been Rebuilding along side the Cardassian Union following the end of the war. Tains Son, and war hero is suspected of helping this project. But all this is just speculation.
Click for Gathered data on the Obsidian Order Pre War
Garak - War Hero and New Chief of the Obsidian Order?