An Augmentation of Arms is an honor added to a registered device, given by the Crown. The augmentation must be registered with the College of Arms.
An augmentation is not registered as a change of armory; instead, both the underlying arms and the arms with augmentation are protected. Therefore, the underlying armory can be changed while keeping the augmentation the same.
Although given by the crown, the crown cannot dictate the form the augmentation takes, though they can make suggestions.