The Crusaders are holy warriors of the Adeptus Ministorum, chosen from the wards of the Schola Progenium for a devotion to the God-Emperor so fierce that it defines their every waking moment. Each is bound by a solemn and unbreakable oath to protect a single master, most often an Inquisitor or a priest of the Imperial Creed, and that oath becomes the whole of his purpose, a vow he will honour with his life without a heartbeat's hesitation.
Yet a Crusader is far more than a living shield. He is his master's right hand in the thick of battle, the blade that turns aside the blow meant for his charge and delivers the killing stroke in return. Clad in heavy armour and bearing a master-crafted power sword and a storm shield, he plants himself amid a press of enemies and simply refuses to fall, an island of unyielding faith around which the fighting breaks. Where his master goes, he goes; whatever threatens his master, he destroys.
Because the Decree Passive forbids the Ecclesiarchy from raising armies of men under arms, its priests may gather only small bands of such protectors, the Battle Conclaves that attend them into danger. Many Crusaders are drawn from the Frateris Militias that muster across the Imperium or from the household guards of the Adepta Sororitas, and all share the same seething hatred of the faithless, the same certainty that to die guarding a servant of the Emperor is the finest death a mortal can be granted.