Bellatrix nodded, staring intently into the room. "I think we've got evidence that our theory may be correct. He could have made a horcrux and hidden it here, too. He may have even used an object that belonged to the family."
"Perhaps," Harry conceded, beginning to feel a faint tinge of excitement. If Bellatrix was right, then he had already made more progress against Voldemort than the Order ever had in his version of the future.
"I don't know if we can get past the dark magic safely," Bellatrix said, but I can cast a diagnostic spell to see what we're up against. If it's so bad that we can't do anything, we can come back later and be more prepared.
"All right," Harry said.
Bellatrix drew her wand, stepped back from the room a little bit, and delicately waved her wand at the room. A sluggish shockwave white light emanated from her wand and pushed into the room. It revealed a myriad of colors and spell weaves, as well as a number of runes on the floor.
"That's pretty bad," Harry observed, not needing Bellatrix's professional opinion to assess the severity of dark magic protecting whatever it was Voldemort was hiding.
"I think we're going to need help getting past all of this," Bellatrix sighed.
"I see," Harry said, his brow furrowed. "What does it take to destroy a horcrux?"
"I'm not sure," Bellatrix admitted. "I probably should have researched that more extensively. I can do it later, before we come back."
"I'm just thinking that fiendfyre is pretty effective," Harry observed. "I could set the house alight and it might destroy the horcrux if it is on the premises. If it doesn't, won't the fiendfyre burn through the materials to which the dark magic protecting the horcrux is anchored? Then we'd be able to retrieve the horcrux out of the ashes."
"That's a pretty good idea," Bellatrix said. "But if we burn down the entire house and the horcrux is susceptible to fiendfyre, we'll never know whether there was a horcrux."
"I didn't think of that," Harry grumbled.
"Here's an idea," Bellatrix said. "How well are you able to control fiendfyre?"
"Pretty well, if I'm not magically tired," Harry responded.
"Why don't you send a burst of fiendfyre into the room?" Bellatrix suggested. "Just enough to burn a centimeter or so off of every surface. That could destroy the wards. We then can assess whether that helped the situation any."
"Good plan," Harry said. He drew his wand as Bellatrix stepped further back from the entrance.
Harry took aim and let loose a wave of fiendfyre. Almost as soon as he cast it, Harry jerked back his wand, twisted it, and attempted to turn the fiendfyre in on itself. It proved difficult, and Harry was sweating profusely by the time he had extinguished it.
Bellatrix examined the damages as Harry caught his breath. "Looks like you may have ended up burning two or three centimeters. It was to be expected, though. Fiendfyre isn't exactly a precision tool."
"Did it do any good?" Harry asked.
Bellatrix was just in the process of casting the diagnostic charm when Harry's scar began to twinge rather intensely. Without wasting a moment, Harry grabbed Bellatrix and attempted to apparated the two of them away from the Riddle house. Unfortunately, there seemed to be anti-apparition wards in place.
"What's wrong?" Bellatrix gasped, knowing only that Harry had attempted and failed to apparate them away.
"Voldemort is here," Harry said tersely.
The tinge grew stronger. Knowing that Voldemort must be in the house, Harry looked toward the staircase and cast a reducto charm. It hurled toward the staircase and the wall beyond, but was abruptly blocked by a shield. A stunner came Harry's way as both Harry and Bellatrix dropped to the floor.
As soon as it passed, Harry shifted and aimed in the darkness toward Voldemort's apparent location. "Expelliarmus!" Harry yelled, resulting to his old standby. In the air, Harry's disarming spell met with a killing curse from Voldemort. The wands being brothers resulted in the Priori Incantatem effect. Harry and Voldemort's wands connected. Red light shot from Harry's wand and green from Voldemort's.
The spell beams lit up the hallway, revealing clearly Voldemort's position next to the top of the staircase and highlighting Harry's unfortunate position on the floor. Determination showed on Harry's face while what might have been fear and consternation showed on Voldemort's
"Who are you, Harry Ashworth?" Voldemort cried above the roaring of the spell beams and the echo of phoenix song. "How did you know of this place?"
Knowing that his focus was essential to winning the Priori Incantatem battle, Harry declined to reply, but focused on pushing the center of the beams toward Voldemort's wand.
It was not merely a duel between Harry and Voldemort, however. Bellatrix was there, too. "Avada Kedavra!" Bellatrix screamed. A green ball of light zipped toward Voldemort. Narrowly, he dodged, wincing as it exploded into the wall, sending shards of plaster and wood flying back.