Vexilla Imperius
Vexilla Imperius are Custodes Vexillas that are carried by the Adeptus Custodes' Vexilus Praetors Standard Bearers. The Praetors are infused with mysterious crypto-technological abilities that aid their brethren and allies in battle, but which abilities come to the fore depend on the Standard they carry. In the case of the Vexilla Imperius, it allows the Praetors to increases the damage the Custodes' weapons deal in battle.[1]
The Vexilla Imperius is the most common pattern of Vexilla. It fills nearby Custodians with inviolable determination and lends fresh strength to their limbs. Whether this effect is purely psychological, or if there is some crypto-technological aspect to the phenomenon, is unknown beyond the Tower Aquilane. It is enough that it works, and works well.[2]
