The magic of the Augustan Brotherhood is a bit difficult to summarize, but I'll give it my best shot...
Fluff: 80 or so years ago, a hedge wizard rediscovered Virgil's Tomb in Naples and found therein a magical book which he used to initiate himself into Virgil's magical system. He then recruited other Gifted scholars (like all the traditions in RM, the Gift is necessary to learn Virgilian Magic) creating a secret society dedicated to recreating the glories of Rome. They hope to accomplish this by serving as Court Wizards and subtly influencing their employers to support the Holy Roman Empire.
Crunch: Virgilian Magic is predicated upon three practices:
Animo: Allows the wizard to invest magical energies into items, effectively creating Magic Things with Vigilo effects as powers.
Sortes Virgilianae: A sort of beefed up version of the "Divination and Augury" virtue, using a copy of the Aeneid.
Vigilo: Spellcasting. All vigilo rites are wards in that they target places rather than individuals - they can either be straight up wards like "Circle of Beast Warding" or more like Watching Wards in that they cause a magical effect to occur when a specific condition is fulfilled.
Example: A wizard might perform a rite designed to cause heavy rain if his city catches on fire.
Initiation into the tradition grants access to the Animo and Sortes Virgilianae supernatural abilties and the six schools used in performing vigilo rites - School or Boreas, School of the Naiads, School or Prometheus, School of the Stones, School of the Sylvan Dryads or School of the Vigilant Bees (these are difficult arts and correspond to Auram, Aquam, Ignem, Terram, Herbam and Animal respectively). A score of 1 in a school allows a wizard to learn any rite associated with that school regardless of its EF, but each rite must be learned individually as an Art with it's score being the main contributer to the casting total.
Because their rites take a long time to perform and can't directly harm humans in any event, the Brotherhood aren't much of a threat in combat. Nevertheless, messing with them could be considered Interfering with the Mundanes due to their association with the nobility and they are good on defense - able to surround themselves with all sorts of magical traps in relatively short order.
I sincerely hope this helps, but these guys are difficult to summarize...