The Turbulent North
The History of Sertrous and the Vanguard
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 10 rake 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 nor to be. Even as Sertrous began his ascent to divinity, he and a number of other ancient demons faced an uprising oft heir 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 entry 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 mortaIs, using them to explore this strange new plane.
As the world grew civilized and worship of its deities spread, Serrrous’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
labour 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, bur 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 Serrrous’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 neighbouring 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.