Then there was Death, behind him. Eternal, ageless. Waiting.
"There is good in you, Harry," Dumbledore whispered. He closed his eyes, serenity carved into his skin. Acceptance.
Harry whispered the spell.
A sudden, sharp pain shot up his spine, bursting from his chest and sending him crashing onto his hands and knees. With a rending slash, a part of him tore from his being. Harry could not help but gasp and fall face-first from the pain. The tearing continued, shredding him until he could only grip the smooth rock beneath him and pray for it to stop.
A swirling mass, pitch black and pulsating, burst from his body. It unfurled like a ribbon, a magician's trick of neverending rope - more and more of it pulling from his chest. Through tear-fogged eyes, he watched Death swirl the long, trailing mass of Harry - of his soul, he realized with abject horror - into the current floating around the Deathly Hallows.
Death intoned in a language ancient and long forgotten. His soul disappeared into fine mist and the floating Hallows settled to land gently beside Harry's fallen form.
Bubbles erupted from the water and the corpses of the inferi rose to the surface. Bloated and floating on their stomachs, they surrounded the small island at Death's silent command.
Then Death was standing in front of him, so close that the thick fabric of its robe brushed against Harry's skin. A skeletal hand emerged from the robe and rested its palm across his forehead.
Harry felt only power and pain.
Everything went hazy; fiery lightning arched across his bones and his nerves. Pain beyond anything he'd felt - beyond the unrelenting burn of the torture curse, beyond comprehension. His mouth opened to scream but the words choked up in his throat, every inch of him tensed and twitching. Harry forced his gaze up to Death's hood. He could not see anything underneath the dark cloth, but he knew, without any doubt at all, that Death was smiling. Harry tried again to whimper, to beg, to do anything, when his heart cracked under the pressure and he died.
...
He woke with a gasp. Tears clouded his vision and every muscle, bone, and cell in his body burned. Instincts screamed in a klaxon warning. His stomach revolted. Every ounce of him shuddered and shook with tremors. All of him screaming wrong wrong wrong.
There was something soft across his back, slowly drawing his focus away from the pain. The fabric of the Cloak nestled against his cheek, pulling him out of his mind and back into reality. Clenched in white knuckles was the Elder Wand, and nestled on his finger was the Stone. They hummed and shimmered waves of magic across his body. Ancient yet familiar, comforting. The Cloak tightened like a warm embrace.
Searching for stability, he felt for the dark magic radiating out of his horcrux ring. It was silent and empty. Panicking, he cast his magic outward. Unbidden, a massive, rolling wave of fire billowed around him, setting the surface of the water aflame along with the empty husks of inferi piled like a floating trash heap. Their undead hearts were no longer beating a cacophonous unholy rhythm. In fact, it was unnaturally still in the cave.
The darkness that had painted every atom of rock and oil-black water, darkness so strong it curdled on his tongue, all of it was gone. All traces of Voldemort's magic dissolved. Swept up in a riotous hurricane and vacuumed, it felt like, entirely into Harry's being.
"W-what?" His voice was sore and strained from screaming.
"Ah, good. You're finally awake," The hem of Death's robe came into view. On shaking jelly-like limbs, Harry forced his body upright, clinging to his Cloak. Across him, half-hidden behind the pedestal lay Dumbledore's prone body. In front stood Death. Its hood was down although that did little to help him gain any sense of expression or feeling from the being. "I apologize. I had not realized the transformation would be that painful."
"Transformation?" Harry whispered. He desperately wanted water but did not have the strength to unclench his taut muscles to summon some.
"Yes. Congratulations, Master of Death."
"What happened? Did you destroy my horcrux?"
"Your soul is intact once more, just not in there." It pointed to his chest. Death sat down across from Harry, leaning back on one elbow and crossing its legs. "You have evolved beyond mortality."
Harry paused to rid his sinuses of thick mucus. Gasping, he said, "I don't understand. You never said this would happen!"
"Well, I didn't not tell you this would happen," Death said casually, dipping its fingers in the water and letting a droplet traverse down its bones. "I told you there would be a reciprocation. I gave you knowledge, you became the Master of my Hallows, I granted you further unspeakable power, and you -" Death's skull tilted, jaw clacking in an ominous, macabre grin. "You will return the favor again."
Harry protested. "I didn't ask to make another deal. I'm pretty sure I just fucking died."
"Oh yes, you did. But only briefly. Don't you feel the power I have granted you?"
Harry felt pain, mostly. Overwhelmed. Pissed. A lot of things, really. Powerful?
The Cloak shuddered around him. It hummed and whispered and faintly, along the far edges of his mind, he felt darkness creep in. He could feel it all - like something had clicked and opened a hidden door. The Wand, buzzing with energy, eager and excited. The Stone, melancholic, hopeful. The Cloak, absolutely pleased with its perceived success and clinging to Harry with an almost familial embrace. It sent him a rush of affection.
His gaze turned toward Dumbledore's corpse. With one absent tug, he pulled on marionette strings and before his eyes - wandlessly, wordlessly, without ritual - Dumbledore rose from the dead, his eyes uncannily dull. Otherwise, the man looked normal, sending Harry a warm, polite smile as he adjusted his glasses.
"Harry, my boy. How are you this fine evening? Not getting into any more trouble, I hope?" He asked calmly.
"Uh, what the fuck?" Harry said.