You stand atop a small rise. Before you lies a wide river valley nestled between a range of forested hills. Why are you here? What happens next? That's entirely up to your group of adventurers as you face the dangers in the Fortress of the Yuan-Ti . Dungeon Masters are welcome to explore a few excerpts from this adventure. (For more from the Introduction, please read the August 2007 Previews!)
WHAT YOU NEED TO PLAY
Fortress of the Yuan-Ti is intended for use with the core rulebooks of the Dungeons & Dragons game. You need the Player's Handbook and Dungeon Master's Guide to play, and even though this book includes statistics for all the monsters in the tactical encounters, the Monster Manual remains a helpful resource. The tactical encounters draw from various sources, including the various Monster Manual supplements (MM2, MM3, MM4, and so on), but all the information needed to run the adventure is provided in these pages.
PREPARATION
This adventure takes place mostly within Castle Serastis, headquarters of the Vanguard of Sertrous. If the players have just completed The Sinister Spire , they enter this adventure by stepping through the electric gate in Fadheela's lair, hidden within the Necromancer's Spike. If you have not played The Sinister Spire as a precursor to this adventure, the party can be led to the area by campaign hooks of your own devising.
The PCs begin the adventure atop a small rise, looking out over a valley dotted with buildings and farms. The ominous Castle Serastis stands within a hollow in the cliff that marks the south side of Cettrux Hill.
Read through the adventure to gain familiarity with the material. Though this scenario has been designed specifically for lower- and mid-level characters, it is by no means an introductory adventure. It is assumed that you have at least some experience as a DM. However, you are likely to run this adventure over the course of several game sessions. For your initial sessions, you can pay more attention to the early encounters than the later ones. In a typical 4-hour game session, you should anticipate getting through three to five encounter areas.
USING THE FORMAT
The encounter format used in this adventure uses keyed entries similar to other published adventures. However, tactical encounters are separate from story information.
Tactical Encounters: Numbered, or keyed, areas are described in the initial section of this text. Use the keyed entries as both a summary of the adventure and a flowchart. If a keyed entry involves combat or other action that places importance on position and movement, that entry refers you to a tactical encounter.
A tactical encounter's page or pages include a map of the area in which the encounter takes place, notes on setting up the encounter, monster statistics blocks, and text descriptions of how the terrain and features of the encounter affect play. Every aspect of an encounter need not be used -- the players might not be interested in all the details of an area. Indeed, the characters might avoid whole encounters, either intentionally or unwittingly.
The combat encounters in this adventure are designed for use with D&D Miniatures . If you don't have the exact miniature to represent a monster, or you aren't using D&D Miniatures , just use whatever substitute you choose to run the tactical encounters.
ADVENTURE BACKGROUND
An organization known as the Vanguard of Sertrous recently sent a tomb-robber named Xeron to the town of Kingsholm. North of the town stands the tomb of the forgotten king, an ancient sovereign prophesied to return from death to defend the land against terrible evil. Within the sarcophagi of the forgotten king and the faithful companions who had served him in life were hidden magic items of great power. With those relics, the Vanguard of Sertrous planned to wreak untold havoc. Possessing the remains of the king himself would allow them to prevent the prophecy from ever being fulfilled -- or worse yet, to corrupt it for their own ends.
Xeron and his allies broke into the tomb and made off not only with the magic items, but also with the bones of the forgotten king. Although Xeron was defeated (either by the PCs or another group of adventurers), his allies met up with other operatives of the Vanguard who transported the bones and relics through the depths of the Underdark. The adventurers pursued them through the subterranean city of Pedestal and to the lair of an ancient drow necromancer.
There, they recovered one of the relics and slew a Vanguard operative, only to discover that the others -- and the bones -- had disappeared through a mystic portal. It now takes one more plunge into the unknown to wrest unspeakable power from the grip of the Vanguard, and to return the forgotten king to his rightful resting place.
WHAT THE PCS KNOW
The PCs know all the information provided in the Adventure Background, above. (If they played through DD1 and DD2 , they know the specific details of those adventures, of course.) They also know, or can at least surmise, that the bizarre fortress is the final destination of those they pursue. Whatever the fate of the stolen bones and ancient relics, it unfolds here.
WHAT THE PCS DON'T KNOW
Before history was even a notion, a demon prince named Sertrous ruled brutally over one of the Infinite Layers of the Abyss. Hateful and predatory even by Abyssal standards, Sertrous was among the first demons to take an interest in the developing races of the mortal world. Hoping to use their worship to ascend to true divinity, he planned to overthrow and consume even the gods.
Fortunately for the world, it was not to be. Even as Sertrous began his ascent to divinity, he and a number of other ancient demons faced an uprising of their Abyssal servitors. Those conspirators not banished to the depths of the plane were destroyed outright. However, Sertrous (along with a few of his minions) fled directly into the mortal world.
Sertrous manifested as a serpentine entity with an insatiable appetite for living creatures. A cult of yuan-ti and feral humanoids formed around the demon, drawn to his strength and inevitably consumed in the name of his hunger. However, Sertrous granted a tiny measure of his own power to a handful of these mortals, using them to explore this strange new plane. As the world grew civilized and worship of its deities spread, Sertrous's own power waned. Eventually, he fell into a seemingly endless slumber. So potent had the demon become, however, that even asleep he observed the mortal world. His hate-filled dreams drove Sertrous to an unearthly transformation -- a manifest evil of the Abyss and the Material Plane, equally bound to both. The cult that had formed around Sertrous (known also as the Slumbering Serpent) split in two. One faction continued to worship the fallen demon lord as a demigod, while the other was driven by those Sertrous touched in dreams -- infected by the demon lord's desire to see the world thrown down and consumed.
The Vanguard of Sertrous
This new cult of Sertrous survived the millennia, though it never grew particularly large or potent. In recent years, however, one of its leaders -- a yuan-ti blackguard named Sulvaugren -- found his dreams touched by a dark madness. Sertrous was ready to wake, and Sulvaugren would be the one to make it happen. Sulvaugren recast the demon's cult as the Vanguard of Sertrous and, with his followers, took over the sect's ancestral home in Castle Serastis. There, he uncovered dark lore describing the Sacrament of the Risen Abyss -- the means by which Sertrous would again walk the world.
The majority of the Vanguard's members believe that they labor to raise Sertrous as a deity, who will then reward them in the new order to come. Only the leaders of the Vanguard know that the cult's true goal is not ascension, but the destruction of all that is.
The Sacrament of the Risen Abyss
This great ritual is the central element to Sulvaugren's plan. Through a combination of blood sacrifice and dark rites, the sacrament forges a bond between the Abyss and the mortal world. Creating that bond requires the remains of a mortal creature with great mystical power. Steeped in prophecy, the bones of the forgotten king best serve the Vanguard's plan. When complete, the sacrament will allow the Vanguard to channel a fragment of Sertrous's dream-self into a creature risen from the remains: a corrupt amalgamation of fiendish and undead essence.
Most of the Vanguard believes that the sacrament is intended to place the spirit of Sertrous into the body of the risen king. After converting his own people to the worship of Sertrous, the king will march at the head of an army of the living and the undead, converting other nations by the sword. In the end, an empire of Sertrous worshipers will elevate the Slumbering Serpent to godhood.
The leaders of the Vanguard know the darker truth. By implanting fragments of Sertrous's dream-self in the risen king, the demon will be able to directly experience and influence the world for the first time since falling into slumber. The forgotten king will indeed use the prophecy to rule the kingdom, but not for the sake of converting neighboring lands. Rather, as Sertrous's influence expands, his vessels and minions will seek additional remains having enough power to repeat the Sacrament of the Risen Abyss. Eventually, enough of Sertrous's dream-self will become active for the demon lord to truly awaken from his millennial slumber. His strength returned to him, the demon lord will rise as an unstoppable being of pure nihilistic hate and godlike power.
DEMONIC HISTORY
If you use Fiendish Codex I: Hordes of the Abyss in your campaign, you know that Sertrous was one of the greatest of the obyriths, and that the revolt of the tanar'ri cast him from power. Whether or not you are using that book, this information is not necessary to run the adventure.