Vlad III Dracula
Vlad III Dracula was prince of Wallacia. Much of his life was identical to what the history books say. Other than the fact that, while in exile, he made a pact with some dark spirits for a second chance at rulership. The nature of these spirits remains a matter of some controversy. But they were powerful enough to aid in reclaiming the throne of his homeland not once, but twice. And then, when he fell in battle against the Ottomans, they rose him again as a strigoi, a leech, a vampire.
After that, it is known that Dracula fled into the shadows of the secret world. He sought out loyal followers and allies and turned them into undead like him. Many of these followers came from Dracula's own knightly order, the Order of the Dragon and these vampires called their new alliance the Sons of the Dragon in homage to both the order, and Dracula's own father, Vlad II Dracul.
The Sons of the Dragon continued their crusade against the Ottomans for several centuries, undermining the rule of the Turks from the shadows. However, they soon found themselves embroiled in a struggle for control of the region against several rival forces, including several werewolf clans and the Cainites, a branch of vampires from the Middle East who claimed descent from the First Murderer.
The Vampire Crusades of the 17th Century saw the Sons of the Dragon (now commonly called the Draculesti) align with several other European vampire factions to drive out the Cainites and other Middle Eastern vampires, as well as breaking the power of werewolves, fairies, and other supernatural beings in Eastern Europe. They were unexpectedly successful, as many of the powers of the region had become complaicent with the status quo. In so doing, the Draculesti became the most powerful faction of vampires in Europe, and Dracula himself became a legend among their kind.
And the Draculesti's rise couldn't have happened at a better time. As their power expanded into Germany, France, Spain and England, those nations were embarking on colonial expeditions across the globe. And the strigoi travelled with them. Four centuries of colonialism later, and the strigoi are the most common form of vampire in the world.
While Dracula was happy to rule his network from his castle in the Carpathians for several centuries, the changing of global politics lead for his relocation of London, where he's resided since the late 1800s. Stoker's own tale tells of this, though in a slightly more fantastical take than the historical truths.
Many of the other leaders of the Draculesti remained in Romania for a few decades afterwards. But they would find themselves faced with their own complacency and the rise of a new threat: communism. The occult divisions of the Soviet Military, including the infamous Red Library, sought to coopt the powers of vampirism for the benefit of the Soviet Union and the global revolution. Much of the Draculesti's leadership fled west, to Vienna, Paris and London. While some have returned to their homeland after the fall of the Iron Curtain, today the capital of the Draculesti is not Cluj-Napoca, Bucharest or Budapest. Instead, it is Vienna, the city that held out against the Ottomans and never fell to the forces of communism.
Dracula, however, remains in London, where he can monitor his global network as well as watch over the politicking of the Veil Treaty that hides beneath the city's streets.