"Let the word of the Emperor be heard once more wherever men gather and look upwards unto the stars. Let them know that the Emperor looks back upon them, from the Golden Throne, wherever in this benighted galaxy they might reside."
- — Cardinal Bloo
A cardinal is one of the highest-ranking priests and prelates within the Adeptus Ministorum, the state church of the Imperium of Man, who serves directly under the ecclesiarch himself. The cardinals, who number in the thousands, are members of the Frateris clergy and form a group known as the Holy Synod, which elects the ecclesiarch, the head of the entire Ministorum, from their own number.
Most cardinals bear responsibility for the spiritual guidance of a region of Imperial space known as a "diocese," whose size can vary from a single hive city to encompass an entire star system or sub-sector of the galaxy. Although each cardinal governs the spiritual (and often temporal) affairs of their own diocese, some cardinals, such as those designated "arch-cardinals," in reality rank higher than others due to the strategic importance or size of the diocese they rule.
This divergence in power is reflected in the fact that cardinals can actually belong to one of three separate orders, as described below. Some of the most important cardinals can also earn one of the three rotating seats on the Imperium's ruling Senatorum Imperialis from time to time.
The five Cardinals Palatine are the highest-ranking cardinals in the Adeptus Ministorum. They do not govern dioceses, instead serving as assistants to the ecclesiarch in the Ecclesiarchal Palace on Terra. It is not uncommon for an ecclesiarch to unofficially designate one of his Cardinals Palatine as his successor at the next conclave of the Holy Synod.
The Cardinals Terran are those cardinals who govern dioceses on Terra. As Terra is the most sacred and politically important world in the Imperium, a diocese on Terra makes its cardinal among the most politically important and powerful individuals in the Adeptus Ministorum. Many an ecclesiarch has been raised from amongst the Cardinals Terran.
The Cardinals Astral maintain dioceses on other Imperial worlds besides Terra. Those in the Ophelia VII region are known as the "Astral Ministra" or "Synod Ministra," while those in other regions are known simply as "Cardinals Astral" or "Cardinals-Astra."
- Codex Imperialis (2nd Edition)
- Codex: Sisters of Battle (2nd Edition), pg. 34
- Dark Heresy: Blood of Martyrs (RPG), pg. 16
- Realm of Chaos: The Lost and the Damned (1st Edition)
- Warhammer 40,000 Rulebook (3rd Edition), pg. 102