Guardians of the Veil is a sourcebook for Mage: The Awakening. It expands upon the Guardians of the Veil, including their history and unique legacies associated with them.

Summary
From the Onyx Path catalog:

"Who are we? Don't ask for secrets if you cannot keep them. Do you wish to take this step? Good. We are the secret police of the Awakened, charged with our task by the kings of lost Atlantis. We watch and judge the Gifted for any sign of malpractice of their Art, for we knew of old that the Abyssal taint of miscast spells risks the very universe. To remain pure, magic must be kept secret - and we make sure it stays that way."-- Coatlicue, famulus Susceptor of the orderGuardians of the Veil is a supplement for Mage: The Awakening.This book includes:

The history, culture and society of the spies of old Atlantis
Factions within the order, the three Veils of initiation and the 49 Masques worn to change identities
New spells, enchanted items and Legacies