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
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