Vigil of Stendarr
The Vigil of Stendarr is an order of paladins devoted to the extermination of Daedra in Tamriel, which was created shortly after the Oblivion Crisis. Each provincial chapter is led by a Keeper of the Vigil. In addition to Daedra, the Vigil also hunts vampires, werewolves, and necromancers, which they see as abominations.
The Volkihar are the most powerful tribe of vampires in Skyrim. The Volkihar are paranoid and cruel, and their breath is said to freeze their victims' blood in the veins. They usually live in eastern Skyrim, beneath the ice of remote and haunted lakes, never venturing into the world of men except to feed. Despite these claims, they are sometimes known to dwell within vampire lairs with others of their kind, and can be found all over Skyrim. They can reach through the ice of their lakes without breaking it to grab unsuspecting victims from the surface. Members of the Volkihar bloodline, like all Skyrim vampires, are infected with the vampire's disease called Sanguinare Vampiris, instead of the more common Porphyric Hemophilia.
Lord Harkon and his family are apparently the progenitors of the Volkihar clan. They are pure-blooded Vampire Lords, having been given the gift of vampirism directly by Molag Bal. Harkon and his court dwell within the ancient Castle Volkihar, on a remote island off the coast of Haafingar, near the border of High Rock.
Volkihar vampires are not a part of one main cohesive organisation. The court, who are ancient and presumably purer vampires, shun the scattered nomadic vampires who are either alone or have nests and factions of their own. The court itself has some in-fighting by power-hungry individuals. The court occasionally kills feral vampires around Skyrim to prevent them either riling the prey, alerting humans to their presence, or to get rid of competition.
Movarth Piquine, once a famous vampire hunter, went searching for the Volkihar vampires and managed to kill one.
In 4E 201, the Volkihar vampire clan grew bold as Lord Harkon sought to find his lost daughter Serana, who was involved in a prophecy which would darken the sun and allow vampires to rule Tamriel. The Skyrim branch of the Vigilants of Stendarr were wiped out in an open attack by the vampires, and raids on major cities were becoming increasingly frequent. To counter this aggression, an ancient order of vampire hunters named the Dawnguard was reformed. The prophecy was realized by Serana and the Last Dragonborn, who retrieved Auriel's Bow and learned how it could be corrupted to temporarily block the sun. Lord Harkon was then defeated with the bow, although it is unknown if the Dragonborn took his place as leader of the Volkihar, or destroyed the court.