Reviewing The Convocation a 5E compatible supplement about Griffon riders written by Matt Click and released by Absolute Tabletop, it is available from Drivethrurpg:
http://www.drivethrurpg.com/product/173201/The-Convocation
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Reviewing The Convocation a 5E compatible supplement about Griffon riders written by Matt Click and released by Absolute Tabletop, it is available from Drivethrurpg:
http://www.drivethrurpg.com/product/173201/The-Convocation