Dead in Thay

Dead in Thay was an adventure module released for D&D Next/5th edition of Dungeons & Dragons, as part of the "Dreams of the Red Wizards" campaign. It was released in April 2014.

Publisher's description
"Szass Tam, the lich lord of Thay, and his Red Wizards threaten to dominate all of the Sword Coast. The Bloodgate, an elemental node of power, must be destroyed in order to stop him. This adventure is part two of the Dreams of the Red Wizards Sundering storyline, directly tied to Scourge of the Sword Coast, and loosely connected to the events in Ghosts of Dragonspear Castle.

Dead in Thay is a tribute to Tomb of Horrors, The Ruins of Undermountain, and other killer dungeons. The monsters, traps, and hazards in the adventure create a deadly challenge."

Summary
Having located Bloodgate Keep, an assault upon it is led out of the Floshin Estates. The elemental nodes that were helping sustain the portal from Thay are collapsed but when an attempt is made to close the Bloodgate itself, Mennek Ariz calls upon Baazka, who transports both him and Shalendra Floshin away. Trying to protect his niece, Kelson Darktreader is caught up in the transportation magic.

The attacking adventurers were whisked away by the Thayan Resurrection to the Doomvault beneath Thaymount. The rebels claim to have saved the party's lives and expect them to repay the favor by destroying the phylacteries of Szass Tam's top lieutenants that are held within.

They venture through the massive and deadly dungeon, locate Shalendra, who was betrayed and imprisoned by her former allies and witness experiments being performed on several captured Chosen before completing their mission.