A Fundamental Ingredient (слэш)

Voldemort, always in search of immortality, uses a ritual to transform himself into an immortal hybrid creature. However, one of the two creatures is a Veela and requires a mate. Voldemort decides that Bellatrix would be adequate for the position of his mate and sends a Death Eater to retrieve one of her hairs to complete the ritual. Unfortunately, his incompetent follower has accidentally gotten the wrong hair and the Dark Lord soon finds himself mated to Harry Potter.