A Nord Vampire Lord and progenitor of the Volkihar vampire bloodline. He lived in a castle on an island a ways away from Solitude with his wife, Valerica, and their daughter, Serana. Lord Harkon was a very wealthy king, but feared mortality. He made a pact with Molag Bal and sacrificed a thousand innocents to the Prince so he and his family could become pure-blooded vampires.
Hidden for many years in Castle Volkihar, Lord Harkon became obsessed with the Tyranny of the Sun, a prophecy that foretold a time when the sun would be blotted out of the sky, shrouding the world in eternal darkness. He sought to carry out this prophecy so vampires could rule Tamriel without fear of burning in the sunlight. To this end, he sought several Elder Scrolls and Auriel's Bow. Harkon's relationship with his family was strained after they became vampires, but animosity between him and Valerica rose rapidly after he discovered the Tyranny of the Sun. Two Elder Scrolls which detailed the prophecy fell into his possession at some point. Valerica, seeking power in her own right, worked to prevent her husband from achieving his ultimate goal. She went into hiding with one of the Elder Scrolls and sealed Serana away in a crypt with the other.
Lord Harkon would search for his wife and daughter until the fourth era, when the Dovahkiin became involved in his affairs. The Dovahkiin, accompanied by Harkon's estranged daughter and armed with Auriel's Bow, slew Lord Harkon in his castle.