The Grey Knights have endured for millennia, their Chapter built upon a web of ancient traditions and oaths. These sacred customs and doctrines are reflected in the weapons they use, the armour they wear and the heraldry they bear, each one a part of their proud history. Grey Knights heraldry is most often depicted upon the portion of their grey Aegis Armour known as the heraldric shield.
Red, white and black are the common colours of almost all Grey Knights heraldry, these being colours used by the first Grand Masters when they forsook their Legions and embraced the sacred duty the Emperor had given them. Each icon and colour has its own meaning within the Chapter; skulls indicate the quelling of powerful daemonic foes and swords battlefield honours, for example as shown above. Crenellated lines, divisions of colour and which colour is ascendant all represent a Battle-Brother's position within his Brotherhood, the colour, direction and gradient of the line or division each having their own meaning.
Grey Knights will sometimes incorporate symbology of their allies into their heraldry if they are especially deserving. In this case the dominate skull above bears the icon of the Inquisition, showing a great victory won over a potent daemonic foe but with the aid of one of the Holy Ordos. However, it is rare for these symbols to be adopted as there are few allies worthy enough to earn the respect of the Grey Knights. Sometimes a Battle-Brother will take the icon of an ally which has been exterminated or mind-wiped in the aftermath of battle. Thus the only reminder of their existence remains upon the Battle-Brother's heraldic shield, a forlorn reminder of their service to the Grey Knights while they lived.
The icon of a sword is a powerful symbol within Grey Knights heraldry. This can represent an act that preserved the Battle-Brother's squad, turned the tide of an important confrontation or brought about the destruction of a most hated foe. A white sword on red as above is a symbol of the Emperor's mercy, an act considered inspired by the Master of Mankind's benevolence. A black sword on red is a measure of the Emperor's wrath and is granted for acts of vengeance