Dumbledore nodded. He hummed and focused, before taking a sure stride north and knocking his hand against a patch of rock no different from the rest.
"Here, I believe, but hmm, another test. He means to weaken any intruders. A blood sacrifice."
Harry groaned. He should have expected something so nefarious.
"Of course, how much is needed?" He asked, resigned to murder the man here and risk not being able to figure out the remaining traps.
Dumbledore sniffed, unimpressed with the whole affair. "Nothing so serious, my dear boy. A slash or so shall do."
"Wait, really?" Harry said. "Not even a limb or something? We should have brought mama, she'll think this is hilarious. A few drops are supposed to weaken a wizard?" He drew his wand and stepped forward before Dumbledore could comment. Harry wiped at the thin cut on his forehead, moving a pearled droplet on his fingertip. He growled out an ancient curse and the blood shimmered a moment, before multiplying too fast to detect, splattering across the rock face. Immediately it sank in and the whole structure shivered and parted to reveal an archway leading to a dark corridor beyond.
"Thank you," Dumbledore said, his eyes surveying the pool of blood coagulating on the floor. His expression was just as calm and even as ever, and he stepped into the next area.
Around the bend, the small corridor opened into a large space, too tall and wide to see the edges of it, not helped by the thick mist clustered in the corners. Harry felt a sudden pang of warning and without thinking, his hand came out to stop Dumbledore, who had moved beside him to gaze at the thick, ink-like black water resting calmly before them.
"Inferi," Harry muttered, bending at the knee to inspect the water closely. "Fucking hell and Hades, there's thousands," he gasped. "Er, pardon my language."
Dumbledore himself swore something fierce, so Harry thought he was excused.
"Thousands, you say?"
"There's so many I can't tell them apart, it's like one big mass," Harry tried to explain. The smell, much more potent and foul than Harry had ever been subjected to, immobilized him. "That's never happened before. They've not been down here a very long time -" Harry pondered out loud. "The decomposition isn't as bad as it should be."
"I did not know inferi decomposed," Dumbledore said calmly, as though they were discussing transfiguration homework. He walked with small, careful steps around the platform, looking for something. Harry meanwhile focused on the chaotic whispers of energy coming from the water.
"They do, much slower than a typical body would. It depends on how much power you infuse with the corpse. You need to keep fueling them. For Voldemort to have made so many, and somewhere this isolated, they would be very weak. I suppose he just accepted that he'd have to top them off when most of them rotted away."
"And you would say he has recently refilled their ranks?"
"Eh, fairly so. Some of them are definitely too fresh to have been done before he got vanquished."
"Hmm, that is worrisome. Alas, we will have to cross the lake to reach the horcrux. We may have to prepare for a fight."
"Please tell me it's not at the bottom, I think I'll have to tap out if that's the case."
The old man chuckled and pointed his rotted finger. Harry noticed a small island, illuminated with eerie green mist. A small something Harry could barely make out sat in its center.
Dumbledore summoned, after a moment of careful maneuvering and muttered spellwork, a small boat that surfaced from the water. It was barely large enough to hold the both of them, rusted and waterlogged and much too precarious for Harry's comforts. They tiptoed inside the vessel regardless.
The boat moved without prompting and Harry watched the inferi drift along the surface of the water around them. He wondered what Dumbledore planned to do should they attack, as the man was remarkably calm for such a scenario.
"You know," Dumbledore said in a measured, lecturing tone. "I believe the challenges in this cave are very telling. There is nothing to be feared from a body, Harry, any more than there is anything to be feared from the darkness. Lord Voldemort, who secretly fears both, disagrees. But it is the unknown we fear when we look upon death and darkness, nothing more."
Harry was not certain this was the right time for philosophical musings.
"A fear of death and darkness are about the worst fears a necromancer could have," he said. "Mama always said that was what kept Voldemort from truly understanding. You can't serve Death if you fear it." Harry tilted up to look at the old man. "Although I would say the fear of the unknown is more about the desire for control."
"Control is a natural craving. But one must accept what is in their grasp. What they can and cannot change. Lust for control becomes a lust for power. Voldemort is obsessed with conquering Death itself but what is the cost? What sort of life has his fear brought him? Nothing but misery and suffering, though he is too stubborn and prideful to admit so."
"And are you scared of the unknown, professor?"
"Ah, death is nothing but the next adventure, is it not? If we knew what was in store for us before our time, it would be much less exciting." Dumbledore responded with a soft grin. "We can be cautious, we can prepare, Harry, but we must not be consumed."
They knocked lightly against the side of the small island.
"Ah! We've made it!" Dumbledore said cheerfully.
The island was formed of black obsidian. A small pedestal stood in the center, emitting oozing green mist and filled with a liquid that Harry was most certainly not going to be drinking.
He inspected the liquid with a careful eye, but with the harsh colored lighting, he had no idea what concoction it might be.