Serana

Serana is an ancient pure-blood vampire and the daughter of Lord Harkon and Valerica. She is known as one of the "Daughters of Coldharbour". She and her family became Vampire Lords after her father made a deal with Molag Bal and founded the Volkihar clan; when this happened is unclear, but it apparently predated the disappearance of the Dwemer in 1E 700.

As a Daughter of Coldharbour, Serana's transformation was unpleasant and emotionally scarring due to Molag Bal's cruel nature. Eventually, Harkon became obsessed by the Tyranny of the Sun prophecy which required the blood of Serana or her mother to power Auriel's Bow to blot out the sun. In defiance of Harkon, Valerica fled with Serana and took two of the Elder Scrolls that were needed to fully understand the prophecy.

Serana was sealed inside Dimhollow Crypt with one scroll, while Valerica hid in the Soul Cairn with the other. Many years later, Serana was awakened by the Last Dragonborn, who had been sent to investigate Dimhollow Crypt by the Dawnguard, and returned to Castle Volkihar. She questioned her father's lust for power and found an ally in the Dovahkiin. The pair ventured into the Soul Cairn to find Valerica and her Elder Scroll, then searched the Forgotten Vale and retrieved Auriel's Bow from two of the last known Snow Elves.

Together, Serana and the Last Dragonborn confronted and slew Lord Harkon. Serana was then free to live out her immortal life how she saw fit. Some say she eventually sought out a cure for her vampirism.