There is no higher calling within the Black Templars than to be named the Emperor's Champion. On the eve of battle, as the brethren kneel before their Chaplains, one warrior among them may be seized by a vision of glorious war and filled with the unshakeable certainty that he has been chosen as the Emperor's mortal vessel upon the field. From that moment he stands forever apart from his fellows, marked out as the instrument of the Master of Mankind's will.
The chosen brother sets aside his own arms and armour and is clad instead in holy raiment. He dons the Armour of Faith, a suit of hallowed plate proof against blows that would fell a lesser warrior, and takes up one of the ten sacred Black Swords the Chapter has borne since its founding. So arrayed, he becomes a living manifestation of the Emperor's wrath, bound by oath to oppose the enemies of Mankind in all things and at all times.
Before the host goes to war, the Champion leads his brothers in the renewal of one of the Chapter's four great Vows, each igniting a different fury in the Templar heart: to suffer not the unclean to live, to uphold the honour of the Emperor, to abhor and destroy the witch, or to accept any challenge no matter the odds. Then he strides ahead of the crusade to seek out the enemy's champions and monstrous overlords, for it is his sacred purpose to face the mightiest foes in single combat and, by their deaths, to inspire the faithful to ever greater acts of valour.