Arthur looked at the ruined island around him and lifted his golden hands. Cracks split the sky, reality folding like glass under pressure. In a blink, the battlefield shifted. They were no longer on Earth but inside the Mirror Dimension.
"The Mirror Dimension?" Mephisto's eyes flicked over the fractured world. "Yao has taught you well."
"Can't have our fight tearing apart this island." Arthur's fingers moved quickly, preparing the next spell.
"I liked the Arthur Hayes I met last time better." Mephisto smoothed his cufflinks, perfectly calm despite the warped world. "Quiet. Calculating. Always looking for an exit. You could have escaped earlier with your friend. But here you stand. Why? No fear? No hesitation? Or have you simply forgotten what I am?"
"I decided to be a Gryffindor for a change." Arthur's voice carried a dangerous lightness. "Fight unfair battles courageously. Knowing you're weakened outside Hell, I thought I'd try blind fighting for once."
Mephisto laughed, the sound wrong in this space, echoes rippling through the fractured air like cracks in a mirror. "You think you can fight me here? Even weakened, I am still Mephisto."
The name itself was a whisper of dread.
The devil struck first—not with flame, but with words that slid into Arthur's mind like poisoned silk. Do you still dream of your parents? Of their screams while you hid in your room with toys?
The attack slammed against Arthur's Occlumency and broke apart.
"This trick again?" Arthur conjured a pack of ethereal wolves that charged through impossible angles. "I made peace with my past long ago."
Mephisto's laugh shattered the constructs effortlessly. "Peace? Is that what you call it? The blood coating your hands from your revenge? The gangsters you slaughtered? The innocent deaths you caused? The families destroyed in your wake?"
Hellfire erupted from Mephisto's hands—not the orange-red of normal flame but a sickly green that burned reality itself. Arthur apparated away, but the fire tracked him, following his magical signature.
Arthur opened a portal in front of himself, redirecting the hellfire back at Mephisto. The demon lord absorbed his own attack with a pleased smile. "Clever. Yao's little tricks. But let me show you real fire."
The entire Mirror Dimension erupted in flames. Not just the ground or buildings—the very air burned. Arthur threw up a mystic shield combined with a Protego Maxima, the golden barrier flickering under the assault.
Through the fire, Mephisto's form swelled, his tailored suit now dressing a monstrous shape. Horns curled from his skull. Shadow-wings stretched wide. His eyes burned with the suffering of centuries.
"This is what you face, little wizard," his voice thundered. "I am fear. I am the darkness in every heart. I am—"
"Can we stop with the psychological games?" Arthur interrupted, having used the distraction to craft something special. "I know it is your style but those won't work on me."
He slammed his hands together, and the Mirror Dimension responded. Every reflective surface—every shard of broken glass, every twisted window, every pooled water—became a portal. Not to elsewhere, but to each other, creating an infinite loop of space.
Mephisto found himself looking at thousands of his own reflections, each one slightly different, slightly wrong. And from each reflection, Arthur struck. Cutting curses, Blasting Hexes, Fiendfyre, even a few of his and SIrius's more creative pranks—a thousand attacks from a thousand angles.
Mephisto roared, hellfire exploding outward in a sphere that vaporized the duplicates, but Arthur had already moved.
He appeared above Mephisto, hands glowing with dimensional energy. The space around the demon lord compressed, reality folding in on itself like the Ancient One had done to him during training. Mephisto struggled against the spatial prison, his form flickering.
"Impressive," the devil admitted through strain. "But I am not merely physical."
He dissolved into smoke, reforming behind Arthur, hand reaching for his soul—
Arthur tried to apparate out of there but some force was stopping him.
Give in, the devil's voice echoed in his skull. Your resistance is amusing but pointless. I've broken gods. What chance does a mortal wizard have?
Arthur's mental shields, honed through years of Occlumency, began to crack. Failures flooded his thoughts. Faces. Screams. Disappointment.
It should've ended there. But the Arthur pinned in Mephisto's grasp shimmered, then vanished. An illusion.
The real Arthur emerged from cover. "Avada Kedavra!"
The Killing Curse, fueled by genuine hatred for this creature that had threatened him, threatened Ariadne, that would threaten everyone he protected, that dared use his parents' memory as a weapon.
Mephisto turned with lazy grace and caught the green light barehanded.
"Good magic." He examined the curse like a sommelier with fine wine. "The hatred is particularly pure. This would have ended that Tom Riddle fellow quite efficiently." He crushed the spell between his fingers, green light scattering like shattered emeralds. "You should have used these tactics against him. Would have saved considerable trouble."
"I wasn't comfortable with that magic earlier." Arthur's voice carried no emotion. "But someone taught me how foolish that was."
"They taught you well." Mephisto's playful mask finally cracked. "But enough games. I have other deals to close."
The Mirror Dimension itself began to burn. Not with fire, but with corruption - surfaces blackening, space rotting, the very concept of reality poisoned by Mephisto's presence.
Arthur felt the wrongness of it, the violation of natural law itself. This was Mephisto's real power - not fire or strength, but the ability to corrupt reality itself.
He had a spell suited for this, though he wasn't sure if it would work.
Reaching deep into himself, Arthur smiled faintly and unleashed it at full power.
"Expecto Patronum!"
A silver falcon erupted, vast and blazing. It soared straight into Mephisto's corruption, colliding head-on. Where Patronus-light met infernal rot, reality reasserted itself. For the first time, the demon lord actually stepped backward.
"Interesting spell," Mephisto mused, eyes narrowing. "Though it causes no damage—"
Arthur wasn't finished. While Mephisto's attention was fixed on the falcon, the real strike came from below. Runes he'd been inscribing with subtle steps throughout the fight flared to life - not offensive wards, but bindings. Ancient sigils meant to anchor spiritual entities to physical space.
Mephisto realized too late. The runes ignited, locking him to the Mirror Dimension, severing his ability to slip through realities.
"What did you—"
Arthur raised his hand, and the Mirror Dimension bent to his will. Gravity flipped, hurling Mephisto upward into the ceiling. Before he could recover, Arthur shifted it again—sideways, diagonal, in impossible vectors. The demon lord's massive form lurched helplessly, tossed like a toy in a world where rules no longer applied.
"You think this will stop me?" Mephisto roared, hellfire detonating outward.
"No," Arthur admitted calmly. "I just wanted to test the new spell. See if it worked."
He felt no urgency. Escape was always possible through Apparition. Until suddenly it wasn't.
Without a warning, a crushing force slammed into his mind—not the subtle whispering from before, but raw will, brutal and suffocating. His defenses buckled as shadow loomed.
Mephisto hadn't teleported. He had simply moved, fast beyond comprehension.
A clawed hand pressed against Arthur's head. No space to run, no time to fight. The devil pulled on his soul.
Arthur screamed, not from his throat but from somewhere deeper. He fought with everything he had, and when desperation peaked, silver light burst from his chest. The Deathly Hallows mark blazed like a star.
The pressure shattered. Arthur Apparated away instantly, reappearing at a safe distance.
Mephisto stood unmoving, though something flickered in his burning eyes. Surprise.
"The Death's Mark," he murmured. "That's… impossible."
"Is it special?" Arthur asked, hand brushing the symbol still glowing faintly on his chest. "I collected three trinkets in the wizarding world. Put them together, got this mark. Pretty powerful. Gave me a few interesting tricks."
"Special indeed." Mephisto's expression shifted through calculation and frustration. "I cannot claim a soul marked by Death. Even I have limits." His smile returned, sharp as broken glass. "But Death-marked or not, you're still flesh and bone. Still killable."
"So it is special." Arthur's eyes narrowed. "Tell me. Does it connect to her?"
"You'll get no answers from me," Mephisto hissed. "And you won't live long enough to need them."
The playfulness was gone. Now every strike carried true intent. Hellfire blasts heavy enough to level cities, psychic pressure bearing down like mountains.
Arthur darted through fractured space—Apparating, folding reality, slipping through portals. His spatial mastery kept him barely ahead of annihilation, but it was all defense. He needed more.
Simple spells wouldn't work. Curses bounced off. Hexes were swallowed in flame. Even Avada Kedavra, hurled with raw hatred, had been crushed like glass. Nothing conventional could work.
His mind raced through possibilities. Who had ever truly hurt Mephisto? Not Strange. Not Scarlet Witch. Only one name surfaced from half-remembered stories.
Ghost Rider. The Spirit of Vengeance who burned Mephisto with his own sin.
It was reckless. Desperate. But it was a chance.
Arthur pulled space inward, hands weaving the mystic duplication patterns. The Mirror Dimension rippled. One Arthur became a dozen. Then a hundred. Every reflection joined them, until Mephisto stood encircled by an army.
"Tricks," the demon sneered. "Do you think numbers matter?"
The answer came in a single, unified cry.
"Expecto Patronum!"
Hundreds of silver falcons burst into being, diving as one. They didn't just shine—they seared with condensed hope, will made manifest. Each pierced Mephisto not in body but in spirit, driving into the corruption that oozed from him.
For the second time, the Hell Lord staggered.
Arthur pressed the advantage. His duplicates converged, hands blazing with new spells. From every side, flames erupted—writhing serpents of cursed fire, Fiendfyre bound by perfect control. The Mirror Dimension howled as the flames took shape: dragons, wolves, serpents, all striking together.
And these flames burned him.
Mephisto howled as soul-fire wrapped his body, Fiendfyre searing even his infernal essence. It was the first true sound of pain Arthur had ever dragged from him.
"Impossible!" the demon roared, his voice shaking the Mirror Dimension itself.
Arthur pressed harder. His true body advanced, wandless hands glowing. With one hand, he fed more Fiendfyre, keeping the demon writhing. With the other, he thrust forward a Legilimency assault—not gentle probing, but a forced reflection.
"Look at yourself," Arthur spat.
The spell struck like a hammer. Mephisto screamed, then froze. His form rippled, cracks spreading across his perfect suit and skin. Through the fissures, Arthur saw not fire, not shadow, but emptiness.
Bound by runes, seared by soul-fire, pierced by memory-magic, Mephisto actually felt pain. His form broke apart into shards of reality, struggling to maintain coherence.
For a heartbeat, Arthur thought: he's breaking.
"ENOUGH!"
The roar exploded like a bomb. The Mirror Dimension convulsed, binding runes shattering under sheer force of will. The backlash hurled Arthur through fractured space, wards barely holding against the infernal blast.
He crashed hard, skidding across broken ground. When he looked up, Mephisto stood once more in human guise, smoothing his ruined suit, darkness leaking from the seams.
"You've impressed me, Arthur Hayes." No mockery now. Just cold, sharp respect. "Few mortals have ever caused me true pain."
Arthur forced himself upright, chest heaving. "Glad to hear it. I aim to please."
"Indeed." Mephisto adjusted his tie, wounds sealing as he spoke. "But do not mistake discomfort for defeat. Here, on Earth, in this fragile pocket you control—you've earned a victory. But I am eternal. Patient. And everyone you care about—the girl, the loyal elf, the boy wizard, the cosmic warrior—they all have souls. Souls that will one day be mine."
Arthur's jaw clenched. "Not if I have anything to say about it."
Mephisto's grin stretched, monstrous. "That's the beauty of it. You can't be everywhere. You won't always succeed. And when you fail—not if, but when—I'll be waiting."
His body dissolved into smoke and sulfur. "Until next time, Arthur Hayes. Do try to keep your friends alive. I prefer them ripe."
"Mephisto." Arthur's voice cut through the fading haze. The demon paused, half-dispersed. "If you come near them, what I did today will feel like a gentle massage. Next time, I'll be stronger."
The devil's laughter echoed across dimensions. "I'm counting on it."
Then he was gone. Arthur stood alone in the warped Mirror Dimension, body aching, lungs burning. He had driven off a Hell Lord. Achieved the impossible.
But Mephisto's parting words lingered. You can't guard everyone forever.
With a gesture, Arthur released the Mirror Dimension, reality snapping back. He stood once again on the northern island, scarred by hellfire but not destroyed. After ensuring it would survive without repair, he apparated home.
The Fiendfyre, the Patronus swarm, the soul-binding runes. Those had worked. But not enough. Not to defeat Mephisto.
And this had been Earth. A weakened Mephisto.
In Hell, Arthur wouldn't stand a chance.
He needed more strength. Any strength.
And he would find it.