In political and administrative system of ancient Rwanda, Abiru or the guardians of esoteric codes were important officials at the court of the king. They served as the advisers of the king, they kept royal secrets, they controlled the symbol of royal power like the dynastic drum, and they enthroned a new king. Their institution was called ubwiru. All the Abiru were not equal. There was something like hierarchy among them. Refering to their power and functions, Abiru were classified as below: * The Abiru- kings: They were two abiru: The first was from Abatsobe family. He was the first powerful Umwiru and was the second after the king. This Umwiru was the head of the national ceremony of Umuganura. The second Umwiru- king was the Umwiru from Nyamweru(place). He was from Abakono clan.
* The Umwiru from Abatege family: He was the second Umwiru in charge of enthronization of the kings and the Abiru- kings
* The pastoralist Umwiru from Abaheka family: he was in charge of taking care of the troops of royal cows. He was the third in the hierarchy of Abiru.
* The Umwiru of the dynastic drum Kalinga: he was the fourth umwiru. He was from Abakobwa family. He was the leader of all the group of all Abiru. This situation was confirmed under the reign of king CYILIMA I RUGWE, but during this period the royal drum was called Rwoga.
* The Umwiru of the drum Cyimumugizi: He was the fifth umwiru. He was from Abatandura family. He was the guardian of the royal drum; Cyimumugizi
* The Forging Umwiru: He was the sixth umwiru in the hierarchy. He was from Abenemuhinda family. He kept the dynastic hummer. These hummers played a significant role in the ceremony of burying the King.
* The Umwiru in charge of keeping the clothes (imyeko) of deceased queen mothers. He was the seventh and he was from Abakuna family.
* There were other cathegoris of Abiru in charge of the following . Umwiru in charge...