A safe, private place to do magick in. Reduces Paradox.
This background applies a .1 reduction of Paradox per point per login, allowing a Mage to bleed off Paradox faster over time.
For RP purposes as well: Any magic done inside the Sanctum is considered 1 less severity for gaining Paradox in the first place. So VN becomes C, and VW becomes VN when making Arete rolls to perform magic.