In the mirror universe, Lord Protector of the Realm was a title in the Terran Empire given to a person responsible for ruling the Empire until the heir to the throne was old enough to assume office. In 2155, Thy'lek Shran planned on declaring himself Lord Protector once he deposed Empress Hoshi Sato and Arik Soong was able to produce a living child from both Shran and Sato's genes. (ENT - Mirror Universe novella: Age of the Empress)