- You may also be looking for Female Changeling (duplicate).
She entered the Alpha Quadrant prior to the mining of the Bajoran Wormhole by Starfleet and was trapped away from her people. She was considered the leader of the Dominion forces within the Alpha Quadrant, though she left much of the organisation and prosecution of the war to the Vorta and senior Cardassian and then Breen military leaders. (Star Trek: Deep Space Nine)
After the Dominion reinforcements failed to appear from the Gamma Quadrant and a vast number of Starfleet and Klingons ships heading to attack Deep Space 9 she ordered all her forces to retreat back into Cardassian territory. (DS9: "Sacrifice of Angels")