Harry isn't all that he seems, he is actually an ancient vampire starting life again in hopes of entertaining himself after years of being alone. When he arrives at Hogwarts and sees Severus he is curious of the man who is almost a vampire himself. Vampire!Harry Slytherin!harry eventually Dark!Harry

Harry is left alone for another painful summer at the Dursleys when he goes through some changes that make him take his life into his own hands. When he arrives at Hogwarts he decides to find someone who can help him with those changes and his loyalties. If his suspicions are correct it shouldn't be too hard after all who comes to mind when someone mentions Vampire.