Auctoritas

Auctoritas: Target is immune to direct effect miracles unless the miracle has a Penetration score equal or greater to the Auctoritas score. Each point of Penetration added to a Miracle increases it's level by 1

What is Auctoritas?
The Auctoritas is the highest expression of Spirit, of a Noble's selfhood. It encompasses an area within about five feet of the Noble in every direction; it is the tie between the Noble and the tree Yggdrasil, where all worlds hang. This mystic shield turns away the magics of other Nobles, Imperators and even Excrucians. When two Nobles aligned with different Imperators each enter the Auctoritas of the other, there is an uncomfortable feeling, like a grating sandstone sound in the mind and in the soul.

Auctoritas in a Nutshell
Auctoritas works like a spiritual armor that protects Characters against direct effect Miracles (though this can be cleverly worked around if the caster uses the Miracle to create desirable effects on the target without the Miracle being foiled by the target's Auctoritas, such as creating an anvil above the target and drop it, figuratively speaking of course, even though this is allowed and encouraged). Only the area surronding the Noble is protected, as the Noble himself can still be affect by the environment.