From publisher blurb:
Storm the Nest of Vipers
Evil yuan-ti conspire to destroy a kingdom using dark rituals and the bones of a long-dead king. To win the day, heroes must storm the yuan-ti fortress and wrest the bones from the cultists' clutches before they complete their rituals and unleash a far greater menace upon the world.
This Dungeons & Dragons adventure is designed for 6th-level characters. It can be played as a stand-alone adventure or as the concluding adventure in a three-part series. (See also DD1: Barrow of the Forgotten King and DD2: The Sinister Spire.) Each encounter contains special tactical information for the Dungeon Master and expanded map features for ease of play.