Avery threw back his head and laughed, a cold, mirthless cackle that echoed through the vast Chamber.
"You think unmasking the tawdry delusions of my heritage will shake my conviction?" he sneered at Harry.
He gestured contemptuously at the twisted Nagini remains and Voldemort bone shards behind him.
"These...were but totems to help focus my hatred, my all-consuming lust for darkness and supremacy over your weak, inferior kind. Though I once let myself believe it!"
Albus's brow furrowed as he tried to make sense of Avery's raving.
As if reading his mind, Avery turned his soulless black pits towards Albus, his thin lips peeling back in a rictus of a smile.
"Allow me to show you the truth of my origins, Potter. So you can fully comprehend the depravity that granted me life..."
He slashed his wand in one sweeping arc. In a swirling eddy of shadows, a massive spectral image began taking shape, looming over the Chamber floor.
Albus felt his gorge rise as the ghostly silhouettes of two figures appeared, grotesquely entwined and writhing. One was clearly the unmistakable form of Rodolphus Lestrange, depraved servant of Voldemort and husaband of the demented Bellatrix. His head was thrown back in ecstasy, fanatic rapture consuming his features.
But the woman beneath him...Albus couldn't tell her face, thrown into shadow as she was. All he could perceive was a jumbled, unnatural knot of cloaked limbs and feral movements, punctuated by harsh growls of mindless hedonism.
"Behold my unhallowed genesis, Potter!" Avery bellowed in macabre delight, his wand conduct the twisted tableau before them.
As the eerie shades continued convulsing and clawing in their throes of abandoned, violent depravity...a third, malignant presence manifested. A miasma of viscous darkness seemed to seep out of the surrounding stonework itself. It hovered over the depraved, rutting forms like an all-consuming black cloud, sucking the very humanity from them.
"I am the spawn of pure, limitless perversion and hatred!" Avery crowed, watching the void's dark tendrils envelop and violate the phantasmal figures. "The offspring of Lestrange's seed, planted in some anonymous Death Eater whore's wanton womb!"
At last, the coiling blackness gave one final, obscene contraction...and suddenly shifted, almost solidifying into the wizened, swaddled shape of a newborn babe. As the specter collapsed in on itself, Avery stood untouched, staring at them with mad triumph in his eyes.
"Conceived from the soulless rutting of the foulest Death Eaters, directly into the gaping maw of the void's malice itself!" he roared, arms extending as if to embrace the corrupt magic that birthed him. "I am the living avatar of darkness unchained, of destruction distilled into its most potent form!"
At last, the haunting visions dissipated into wisps of black smoke. Only Avery remained, chuckling softly to himself as he savored the looks of abject horror and revulsion etched on the Potters' faces.
"So you see?" he purred, baring his teeth. "I require no paltry link to the Dark Lord himself. For I am the truest descendant of the unfettered darkness his weak, aborted reign merely arose from."
His wand rose again, practically thrumming with malevolent power.
"And now...I shall show you b oth just how horrific and absolute my mastery of that darkness has become!"
With a sound like rending thunder, Avery's free hand clutched at his robes and tore them open. There, scored into the ashen flesh over his heart, was a spiral seal of twisting black runes. The archaic symbols seemed to writhe and pulse with eldritch energy.
"Behold the pinnacle of the darkest rituals..." Avery rasped, his voice taking on an unearthly timbre. "The forbidden art of Anima Vincularis!"
Harry's eyes went wide with recognition and horror. Even from his exhaustive studies, he knew that term referred to the most unnatural of bindings - the irreversible act of entombing one's living essence directly within a wand's core.
"You've gone too far, Avery!" Harry bellowed. "Playing with magic that unravels the fabric of one's very soul!"
But the young man seemed past the point of heeding any voice of caution or reason. His eyes had rolled back, showing only sickly whites as he traced the spiral seal with the tip of his wand. A miasma of inky blackness began bleeding out from the twisted runes, coiling around Avery in a vortex of shadows. Albus moved to intervene, but his father flung out an arm, shielding him with his own body. A concussive force emanated out as the vortex contracted, rendering everything in slow motion. Avery's mouth stretched wide in a silent, rictus scream, wand aloft as the black vortex imploded...
...and when the chamber finally stopped quaking, all that remained clutched in his clawed hand was an obsidian-black wand. Its core smoldered an angry crimson, as if imbued with the burning embers of a corrupted human soul. A demented chuckle issued from Avery's lips as he gave the wand of darkness an experimental wave, sending a cyclone of crimson sparks scything through the air.
"Yes...I can feel it! This thing's power is like a nexus of pure entropy, a singularity of oblivion given wanton focus!"
His gaze snapped back to the Potters, bottomless pits of hatred and malice bored into them from the depths of whatever depraved remnants of his humanity remained.
"Face the consequences of opposing one who has transcended the mortal boundaries of magic itself, fools!"
With a sweeping, obscene gesture, Avery seized the tendrils of death magic radiating from the wand. A soul-sundering howl of wind and whispered damnation exploded forth as he directed a vortex of eviscerating force towards Harry and Albus.
Only Harry's mastery of the most powerful shield charms prevented them from being obliterated on the spot. But even reinforced by Albus's own defenses, their combined barrier strained and buckled under the torrent of Avery's malignant onslaught.
"You cannot withstand the full brunt of my wand's unfettered potential, old man!" Avery bellowed in rapturous exultation, redoubling the barrage. "Its dark fire was stoked from the primal void itself! It will not be contained or denied its annihilating essence!"
Fissures cracked across their buckling shield, shards of Harry and Albus's wild defensive spellcasting ricocheting in all directions. They were being inexorably driven back by the sheer, unadulterated force of Avery's unholy magic. In the chaos, Albus met his father's eyes. A lifetime of hardship, sacrifice, and silent strength passed between them. Harry gave a tight nod. Then, with a bellowed incantation Harry drew upon the sum of his decades of magical experience. His wand arced through the air, radiant golden filaments of ancient druidic energy contrailing from its tip. Time seemed to still as Albus witnessed the avatar of the Deepest Magic condensing between Harry's outstretched hands, rapidly growing brighter and denser until it became a miniaturized star - a sun of purifying power that defied rational understanding. The coruscating sphere pulsed in cadence with Harry's chant, which rose to fevered crescendo. With one primal yell of exertion, he thrust the coalesced mystical force towards the oncoming tsunami of Avery's vortex of unraveling annihilation. For the span of a suspended heartbeat,Light and Darkness met in apocalyptic stalemate. Then the sphere of ancient magic detonated, shattering into prismatic lances of pure energy that speared through and scattered the vortex of entropy like a defiant sunrise banishing a storm of chaos and shadow. An agonized cry was torn from Avery as the lances drove through his defenses, impacting him with the full immolating fury of life's regenerative fires.
When at last the blinding cataclysm faded, Albus was stunned to find Avery still standing amid the scorched and blasted Chamber. His robes were tattered and smoldering...yet somehow, the malefic wand remained clutched in his upraised fist, now streaked in virulent red and black ichor. Eyes wide with shock and hate, Avery spasmed and roared - a sound of such guttural wrath and apoplectic fury that Albus instinctively recoiled. He raised the corrupted wand in a shaking talon, its writhing core glowing baleful and malignant. But suddenly, the wand of ultimate darkness shattered into ash and embers, its binding of evil too unstable to withstand the concentrated blast of goodness and perseverance that had struck it. Transfixed, Avery gaped in disbelief at the ruination crumbling from his grip, his twisted face registering only mortal shock at its destruction.
Then, like a crumpling husk, he toppled gracelessly, never to rise again from the broken crater of ruin the Chamber had become. The crown of severance between light and darkness had been sundered - paid in equal toll by both sides. For long moments, only the soft patter of Avery's ashes settling in somber silence could be heard. But when father and son at last made their way across the blasted stone towards each other, twin triumphs of soul-wearied defiance shown in their tear-streaked faces. Without a word, Harry pulled Albus into a fierce, shuddering embrace. For they knew the truest power could never be contained solely in artifacts or spells...
But in the unbreakable, loving bonds between those united to protect this world from the encroaching void.