The Holy Synod is the ruling body of the Ecclesiarchy.
Based on Terra, the Holy Synod consists of the Ministorum's Cardinals, each of whom rules over a diocese. The Holy Synod periodically holds Ecclesiastical Conclaves in which Cardinals from all over the Imperium journey to Terra and discuss issues concerning the Ecclesiarchy. As the Holy Synod determines religious policy in the Imperium it is extremely influential and one or more of the Cardinals on the Holy Synod may represent the organization on the High Lords of Terra.
Alongside the Holy Synod based on Terra, another ruling body known as the Synod Ministra exists on the Cardinal World of Ophelia VII. Although the Holy Synod on Terra remains the supreme ruling body of the Ecclesiarchy, the Synod Ministra acts as a secondary governing body. Located further from Terra, the Synod Ministra relays and disseminates the dictates of the Ecclesiarchy of the Holy Synod, enforcing the laws of the Ecclesiarchy. Secondly, it provides a defense against the manipulation of the Ecclesiarchy by other Imperial organizations such as the Administratum or even a single individual within the ranks of the Ministorum itself. This ensures that never again will a High Lord or an Ecclesiarch have total power over the Ecclesiarchy, as was the case with Goge Vandire during the Age of Apostasy.