Regent

Regent was a title that was given to an individual who rules on behalf of another, typically because the actual ruler has not reached the age of maturity, or is otherwise absent or infirm.

In the mirror universe, the ruler of the held the title of regent as it was believed that they were just acting as rulers until Kahless the Unforgettable returned. A few notable regents were and his successor,, who fermented the alliance between the Klingons and the Terran Empire in the 2290s. ( : ''; : "A Burning House")

The head of the Klingon-Cardassian Alliance was also referred to as regent. In the 2370s, held the title.