Strixhaven: School of Mages features its namesake location of Strixhaven, the most elite University in the Multiverse. Each one of the five featured colleges represents one of Magic's enemy color cobinations: Silverquil (W/B), Lorehold (R/W), Prismari (U/R), Witherbloom (B/G), and Quandrix (G/U). Each college has its own personality with its cards featuring watermarks of that college's insignia.
Mystical Archive is a separate set of cards associated with Strixhaven: School of Mages, with one appearing in each draft booster and set booster, and at least three appearing in each collector booster. In Mystical Archive, Wizards of the Coasts has reprinted 63 of the most famous instants and sorceries of all time in specially designed showcase frames. Mystical Archive cards are not Standard legal unless they were printed in another Standard-legal set. Likewise, legality of these cards in other constructed formats is not changed by their printing in Mystical Archive. However, the cards may be used in Limited events. [source]
Commander 2021 preconstructed decks are released alongside Strixhaven: School of Mages, with each deck featuring one of the Strixhaven colleges. These decks include brand-new cards not found in Strixhaven: School of Mages and many reprints of Commander favorites.