Wilderlands Age of Worms
Drazzaroth is described in the Runes in the Well of Triptych Knowledge as “the great ally” of the Avolakia, “the Voice of Yog,” “the Consort of the Worm-Faced One,” and “the eternal dragon.” The party has surmised (correctly) that Drazzaroth might also be the red dragon that stole the monolith from the top of the Spire of Long Shadows, as they observed in the second vision they saw at Kuluth-Mar.
More recently, the party has learned that Drazzaroth is a dracolich. They found his phylactery in Kongen-Thulnir and destroyed it. Soon they may have to face him.