The land of Thay is a forbidding place. Thayan slavers scour Faerun for the unfortunate and dispossessed, returning them to Thay to auction to the highest bidder to keep in motion an economy that rides on their backs. Factions of Red Wizards, all of them outwardly bearing fealty to the Lich lord, Szass Tam, scheme and plot, constantly seeking to undermine each other and grab as much power as they can for themselves. Armies of undead and transmuted living creatures are generated off assembly lines under Szass Tam's rule, as he plans to defeat the Lords' Alliance, conquer the Sword Coast, and install himself emperor of Faerun. His longtime vampire assistant, Esrelda Yeth - Tharcion of the Larpendrar province in Thay - seeks to execute his plans and gain favor in his eyes.
Here is the Episode 8 that Rise of Tiamat should have contained! Thay in all it's horrid and far-reaching power and might. A society dark, alien, at odds with itself, and at the boiling point of explosion.
This adventure is meant for characters between 11th and 15th level, and there is material here sufficient for 5 or 6 sessions of about 3 hours each of play. The material has been playtested once : when I DM'd it for my home campaign with my friends as a replacement for Episode 8 of Rise of Tiamt. You could also run this as a mini-campaign after Rise of Tiamat as a kind of epilogue - instructions are provided on changes to do that or to run it as stand-alone.
Also provided are over a dozen combat maps, as well as a hex map of the Nethwatch Keep area of Thay. You can run this as a sandbox, or as a linear adventure - provisions are given for both options. There are 3 "dungeon delves", a well-developed village, and several wilderness encounters. Two rumors tables assist with advancing the adventure if it's ran as a sandbox. NPC's are provided with goals and how to evoke their personalities. There's also a section with a new monster (Draco Skeletons) and a couple of new NPC types (including Thayan Bladesingers) stat'ed out, as well as a new magic item. A new presentation for NPC spellcasters is also provided, to allow more easily running them in play.
There are 127 pages of pdf content here, split into 5 pdf files for easier downloading. The first 34 pages of the first pdf file are available in the full-size preview.
In addition to the core rule books, you will need Volo's Guide to Monsters in order to run this adventure. Please check it out! I think you'll like what you find.