The Council of Apostles was the ruling body of the Amarr Empire prior to the Moral Reforms. In those days, the Emperor was the head of the Apostles Council, as first among equals.
The Council was at one point usurped by Zaragram II, who proclaimed himself the divine manifestation of God. After Zaragram's death, the Council did its best to erase all history of him and for a short time became extremely powerful. This power eventually led to the Moral Reforms.
It was dissolved during the Moral Reforms, where much of its powers were transferred to the Emperor and the Privy Council. Many of its records and artifacts were preserved by the Order of St. Tetrimon.