Akirian are one of the independent civilizations in Master of Orion.
You find the planet inhabited by the pious Akirians, a race of aquatic beings who have forsaken technology in search of spiritual illumination. They claim to live in peace and harmony with nature, but they know full well the dangers their holistic existence faces when confronted with the might of visitors from beyond the stars.
A diarchy, or duumvirate, is a system where power is shared by two people with equal power, each having veto power over the other's decisions. However, the game only mentions "Trakshal" as the leader title. It is possible that "Trakshal" is their designation for both corulers at the same time. Historically, diarchies tend to appear as a compromise when two monarchs with equal power or legitimacy claim rule over the same land or people.