Published by White Wolf in 1999 as part of its line of supplements for Vampire: the Dark Ages, the 94-page Cainite Heresy provides details on a heretical sect within the vampiric world. Part of the apocalyptic "Year of the Reckoning" line of World of Darkness products that traded on real-world millennialist fears, this book is clearly marked on the cover as "For Adults Only" and was published under White Wolf's "mature content" imprint, Black Dog Studios. As the disclaimer quoted above indicates, this book earns this moniker, both in concept and execution. (As is usual for Black Dog publications, there's more than a bit of nudity scattered throughout the illustrations.)
"Note: The author of The Cainite Heresy believes that Jesus Christ was the Son of God. Nobody remotely involved with this project, or at White Wolf, believes he was a vampire." How is that for an eye-catching disclaimer? Kenneth Hite, recently named Lead Designer for the new edition of Vampire: the Masquerade, serves up his trademark mélange of hidden history, deep conspiracies, and high weirdness as he describes the eponymous Heresy and how to use it in your own Dark Ages chronicles.
Hite and his team examine what happens when purportedly Christian vampires begin combining real-life gnostic heresies such as Gnosticism (specifically Catharism) with their own supernatural mythology. The answer, in short, is a cabal of vampires who believe they are literally Godly agents of salvation, their vampiric blood a holy sacrament. A "Shadow Church" within Christendom, complete with its own religious leader (the Archbishop of Nod) and administrative structure (the Crimson Curia) leads the Heresy, which spreads through a combination of proselytizing, dark deals in the halls of power, and, most blasphemously, through adulterating communion wine with vitae (vampiric blood).
Due to the nature of vitae, mortals who ingest this unholy communion are cured of their ailments and, after three doses, become the enthralled ghouls of their vampiric masters. This has obvious utility when it comes to growing a flock of true believers, and the Heresy has gradually extended its claws across Western Europe.
The book details the reach and power of the Heresy, its recruitment practices, its history (which largely hinges on a forbidden tome called the Euagetaematikon, or Book of the Shining Blood), and its blasphemous designs (briefly: anxiously awaiting the imminent birth of the "Third Caine" and subsequent end of the world).
Guidelines are provided for running Heresy-centered chronicles, including some helpful guidelines on roleplaying the unshakeable religious faith of the medieval mindset, Cainite or otherwise.
The book rounds out with details of the Heresy's many enemies, both living and undead, a detailed look at the Via Diabolis, and select Storyteller characters.
All in all, the Cainite Heresy presents plenty of material from which to hang several chronicles' worth of stories, for characters both inside and outside the Heresy. With this book, troupes must prepare to confront the dark side of faith: "corruption of the most putrescent kind," in the words of the book itself.
