Colonel Lovok was a Changeling who, in 2371, replaced the Romulan Tal Shiar officer known by the same name.
When Enabran Tain, the former head of the Obsidian Order, proposed an alliance between the two intelligence groups to destroy the Founders' homeworld, the Founder posing as Lovok saw a great opportunity. The Founders were aware that the two groups were ruthless and efficient organizations that posed a great threat to them. By doing everything possible to push this alliance, they effectively led the two groups into a trap that would reduce their capabilities.
During the Battle of the Omarion Nebula, Lovok helped Odo and Elim Garak to escape from Lovok's Warbird, stating his reason, "Because no Changeling has ever harmed another." (DS9: "The Die is Cast")