The first and most simple rule of the Darkness is that it must consume all Light. And what better than from the very souls of the Light's servants? The character has an Unseen Sense [CofD 60] for the Light. This sense registers all Light-touched characters and objects - Blessed Places, Nobles, Shikigami, Sworn, Beacons and Bequests. This Umbra is responsible for many of the Darkness’ most cruel attacks.
Drawback: However, the rule of Darkness works in reverse - The Light must redeem all Darkness. Any Light-touched character who triggers the Unseen Sense feels a sensation of being watched by enemies even if they can’t see the character. If the character pinpoints another character as Light-touched, the target automatically recognizes the character as a Dark creature on sight. Some creatures of Darkness note this drawback and are cunning enough to exploit it, using it to set traps for suspicious Nobles. Most Dark creatures lack this cunning and it’s still a notable drawback.