The Loremaster's Curse

From the Introduction: The Loremaster’s Curse is a standalone encounter designed for five 12th to 14th-level adventurers. The soul of an ancient dragon has cursed a scholar, forcing him to release monsters contained within the books of a long lost library. The players must fight back several waves of legendary creatures before taking on the dragon in an attempt to release the loremaster from the library’s grasp.