The connection between the two wands broke-partially because of Voldemort's dodging Bellatrix's killing curse and partially of his own volition, for he had realized that he was losing the Priori Incantatem battle to Harry.
"Avada Kedavra," Bellatrix yelled again and again.
Harry watched as Voldemort nimbly dodged Bellatrix's killing curses. "Keep it up," Harry told her, hoping that Bellatrix heard.
Resulting once again to fiendfyre, Harry cast it toward Voldemort. If it caught the house of fire, it would be difficult for Voldemort to dodge both the fire and the killing curses. Perhaps if one of Bellatrix's killing curses hit home, Voldemort would be left in condition similar to how he had been after having failed to kill Harry. That would give him and Bellatrix enough time to search out the rest of the horcruxes. Then, they could go straight to Albania where Harry knew Voldemort was wont to hide.
Between dodging Bellatrix's curses and Harry's fiendfyre, it was difficult for Voldemort to fire countercurses, but he was not about to give up. There was too much at stake. He began to retreat down the stairs. Harry and Bellatrix pressed forward, keeping pace as Bellatrix fired curse after curse toward the dark lord.
Seeing that Voldemort was retreating and seeing that the fiendfyre was proving very distracting for Voldemort, Harry realized that if he could distract Voldemort even more, then perhaps the dark lord would lose focus and get hit by one of Bellatrix's curses. With a faint smile of hope, Harry wildly began casting reducto curses at the wall and even toward Voldemort. Debris from the damages began to pile up. With an extremely broad sweep of his wand, Harry banished everything that wasn't human or held down toward Voldemort. Let the dark lord try to dodge that, the fiendfyre, and a few killing curses, Harry smirked as he watched the debris lift in the air and began zooming toward Voldemort.
A sudden cry of surprise from Bellatrix alerted Harry to the fact that something had gone wrong. He glanced back toward her and saw her clutching her hair. Her hairdo had fallen because the hair ornament was no longer in it. Harry gasped and spun back toward Voldemort. He spotted among the debris flying toward Voldemort the magical hairpin.
Before Harry could calculate the possible severity of what had just happened, Voldemort, no longer being forced to dodge Bellatrix's killing curses, jabbed his wand forward and let loose a shockwave blast followed by a banishing charm of his own. Harry's own charm was easily cancelled and the debris Harry had created zoomed toward Harry and Bellatrix at lightning speed.
The wood and plaster smacked into Harry and Bellatrix, cutting up their bodies while Bellatrix feebly tried to cast a shield charm. And then, abruptly, Harry gasped as he felt the hairpin plunge into his stomach. Suddenly feeling weak, he fell toward the floor. Dimly he could hear Bellatrix hysterically screaming defiance as Voldemort laughed and shouted the incantation for fiendfyre.
Bellatrix shot several more killing curses toward the dark lord, but it was unnecessary. Voldemort was retreating, already having written Harry and Bellatrix off as dead. Sobbing, Bellatrix dropped down next to Harry and grabbed the hairpin.
"No," Harry gasped weakly, instinctively knowing that ripping it out could do more damage.
Before either could do anything more, dizziness overcame them both.
END OF PART ONE
The One with the Power to vanquish the Dark Lord shall come… he who is marked the equal of the Dark Lord… he who is tied to the Daughter of the Stars and has altered her path in the heavens… from the seat of the Blacks he will haunt the Dark Lord's paths and have power the Dark Lord knows not… and One must die at the hands of the other, for neither can live while the other survives. The One with the power to vanquish the Dark Lord shall come… ~Sybill Trelawney