Triarch

From gronkfinder

Triarchs are the highest-ranking generals of Iaramnae and the leaders of the nation. As the name makes clear, there are never more than three triarchs at a time, as they draw legitimacy by claiming to be the successors of the three diadochi whose alliance led to the formation of Iaramnae.

Upon the death or retirement of a triach, the other two select a new figure for the role.