Harry’s sixth year at Hogwarts was turning up to be the worst so far. Death Eaters have successfully infiltrated Hogwarts, Dumbledore is dead.
At least he taught Harry the secret to Voldemort’s survival, horcruxes. In the notes left to him by the late headmaster, Harry finds a crushing secret, he carries a shard of Voldemort’s soul within himself. Desperate research with the limited sources available followed, leading him and Hermione to eventually discover a dark ritual. The price would be high, but they found a way to contact Death. A Representative of Death arrived and a deal was negotiated. The horcux in the scar was removed and Harry agreed to hunt the remaining horcruxes.
To make his job easier, the Representative presents Harry with a gift in the form of a black sword capable of destroying a horcrux or an undead with a single cut. However, Harry was tricked, the sword tries to influence Harry’s mind with a compulsion to go hunt the nearest Horcrux along with a pull towards the nearest horcrux. Every day Harry is not hunting the horcrux, the compulsion gets stronger. And as becomes clear later, the deal was to hunt horcruxes, any horcruxes. Slowly, Harry builds up his skills needed for his new life. Fleur joins him in order to protect him and teach him curse breaking.