Strahd von Zarovich

"I am ancient. I am the land. My mortal life is lost in the ancient past, and I am neither undead nor alive. I am a vampire, for eternity. I have ruled this land for centuries, crushed all who oppose me, and you presume to challenge me? You are not prepared."
Overview:
Strahd von Zarovich was the oldest and most powerful Vampire lord known. Once a chivalrous prince and general, he conquered the region now called Barovia centuries ago. After a conflict with his brother Sergei over his love, a foreign princess named Camille, he became a vampire under mysterious circumstances and turned Barovia into a hell of his own making. In the centuries since, Barovia has become a haunted land from which no one - bar the nomadic Vistani - may leave. Until recently, he watched over the land from the dread towers of Ravenloft, waiting for the day his love would be reincarnated and reunited with him once more.
The Power of the Fanes:
Strahd's power over Barovia was absolute. His control stretched as far as the animals, the plants, and even the weather. But it was not always so. Once, a trio of nature goddesses, the Ladies Three, watched over the land. Before Strahd's conquest, the inhabitants of the valley, a mixture of druidic barbarians and settled folk, worshipped these goddesses and called them the Fanes. The Huntress kept watch from the mountains, looking after the dead of the native folk and blessing some with werewolf lycanthropy. The Seeker kept watch over the woods, anticipating the future and watching over the valleys with ravens. Finally, the Weaver held court in the rare fetid bogs of the land, holding the memories of the past.
When Strahd solidified his rule over the valleys, forests, and mountains of Barovia, he could brook no opposition to his rule. He desecrated each of the most holy sites of the Fanes, siphoning their power for himself. The remaining Cerunni - the Forest Folk - were made to worship Strahd or be slaughtered.
History:
Centuries ago, House von Zarovich ruled a sizeable domain stretching from Lornham to the western border of the Empire. Strahd, the eldest son of King Barov von Zarovich, was a powerful wizard and key general in the latest waves of expansion. He crushed the dusk elves with an iron fist, and helped the kingdom grow to its greatest extent.
But Strahd desired more. He set his sights on the weak nation of Delmor, who occupied picturesque alpine valleys ripe for the taking. His armies marched forth, and carved out a realm of his own. He crushed their armies easily. He fought the Order of the Silver Dragon, and prevailed. Finally, his conquest complete, he invited his family to admire his accomplishments, to see the great castle he was raising in their name.
Strahd's family disappointed him greatly. They arranged a wedding with a beautiful foreign princess, but not to Strahd. Instead, they betrothed her to his younger, handsomer, layabout brother Sergei. The princess, Camille, arrived at Ravenloft well in advance of the von Zarovichs' and during their time together, Strahd fell in love.
What exactly happened at the wedding is shrouded in mystery. What is known is that Sergei was killed, Camille disappeared, and Strahd did not die when pierced by the arrows of his brother's guards. Later, adventurers in Barovia discovered that Strahd stumbled across a sarcophagus of the dread goddess Sanguine in an ancient Temple. Forging a pact with this power, he gained the power of higher vampirism, and was thus rendered immortal.
Downfall:
In the waning months of the 735th year of Holmgardian reckoning, a group of outlanders was invited to Barovia by Strahd himself. This was not an unusual occurrence, for Strahd often lured unwary warriors to his realm for the purposes of entertainment. Among these adventurers were the two half-elves Cressida Asgard, a student from the Imperial College in Amon, and Caithus Davril, an acolyte of Kelemvor from the recently glorified city of Carovin.
The outlanders traveled across Barovia attempting to escape from the mists and defeat the vampire, and came across Irina Kolyana, whom Strahd believed to be his long-lost love, Camille. Later, near the Wizard of Wines, they were joined by an adventuring Halfling: the bard Mim Proudbottom.
Losing some of their friends in the process, the four travelled throughout Barovia, slowly uncovering the secrets to Strahd's power. They restored the Fanes, uncovered lost artifacts, and made allies.
At last, they marched on Ravenloft. After a period of cat-and-mouse, and a frantic running battle through the ancient fortress, they overcame Strahd, nearly perishing in the process. And so the sun rose over Barovia once more.

A Capricious Dreadlord:
The Lord Protector, as Strahd styled himself, was a patient and calculating foe. His long centuries of power gave him a mixture of unshakeable confidence and patience. He was in no hurry to dispatch "threats" to his rule, for they gave him purpose and entertainment with which to pass the long decades. No. He had no need to kill his enemies right away. Much better to toy with his foes, make them think they have a chance, before slaughtering them - or worse. Such was the fate of countless adventurers foolish enough to challenge the Devil Strahd.