Skyrim: Lord Harkon

Skyrim Dawnguard: Lord Harkon Human Form

Skyrim Dawnguard: Lord Harkon Vampire Lord Form

Lord Harkon is an NPC in Skyrim: Dawnguard

He can be found in Castle Volkihar

Harkon is the leader of the Vampires. He is the father of Serana and husband of Valerica

You first meet him during the quest Bloodline. He offers to turn you into a Vampire Lord