I detail two of the big villains of the Sibersk area of Krevborna below. This is one of the largest revisions of this bit of the setting; previously, Countess Alcesta was the undisputed ruler of the "vampire adventure" area of Krevborna, but now I'm convinced that having two powerful vampire lords who intrigue against each other offers so much more opportunity for drama and intervention by the players' characters.
While I'm here, I thought I would answer an interesting question someone recently asked me about Krevborna: "How are Krevborna's Big Villains different from Ravenloft's Darklords?" To my view, in Ravenloft each domain is an extension of its Darklord. In the earliest box sets for the settings, most of the world-building is tied up in the Darklords' tragic backstories. Each domain is a custom prison cell containing and frustrating the Darlord who lies within it; each domain is a reflection of their evil.
In contrast, each named villain in Krevborna is an exemplar of what's wrong with that region of the setting. For example, both of the vampire lords below are personifications of the feudal, class-based anxieties that Sibersk is meant to explore.
Alcesta von Karlok is a masterful gatherer of information and an adept manipulator. Alcesta favors indirect machinations; she prefers quiet assassination and complex stratagems over blatant aggression. She regularly holds salons in Castle Siebenhurst to stave off boredom and keeps a harem of beautiful, intellectual, and artistic men and women to provide her with whatever stimulation she requires.
• Appearance. She is a breathtaking, red-haired beauty who refuses to be dressed in anything less than the height of fashion.
• Personality. She appreciates witty conversation and demands to be amused by those around her.
• Motive. She wants to be privy to every secret and experience every possible pleasure—no matter how base or degenerate.
• Flaw. She detests the inescapable ennui that comes with long centuries of undeath.
Magnus Draghul only ever truly feels comfortable when striding across the battlefield clad in his blood-red armor and giving vent to his violent impulses against whoever dares to oppose him. Magnus has few close relationships, but his most trusted advisors are his three vampire brides: Lilandra, his cunning spymaster; Phaedra, his private assassin; Maxima, his military strategist.
• Appearance. He is a towering vampire of rigid, militaristic mien, with a long mane of hair, a sweeping mustache, and piercing eyes.
• Personality. If a subordinate does not bow and scrape before him, they will learn a grievous and painful lesson.
• Motive. He is driven to seek glory through military victory.
• Flaw. His belief in the superiority of his martial skill sometimes blinds him to obvious danger.