"Beneath the fractured crust of the mortal plane, beyond the reach of gods and the judgment of angels, there exists a world unshaped by order or mercy. It is the Underworld. The Demon Realm. A land forged by chaos… and ruled by the shadows of the beginning."
The screen fades from darkness to a sweeping view of the Underworld. The sky bleeds red, streaked with ash clouds and roaring black thunder. The very air is dry—parched of life and soaked in malice. Demonic sigils float like drifting embers across the air, whispering curses in forgotten tongues.
Low, guttural winds howl through the jagged valleys. Cracked mountains ooze with molten sorrow. Rivers of black ichor slither through crimson soil. At the core of this abyss stands a colossal, scorched continent known as Draz'Val'Thun—the Heart of Despair.
Here, on this desolate throne world, the Primordial Demons dwell—rulers of their own corrupted dominions, each commanding a lineage of daemons born from the raw will of the Underworld itself.
A land of constant eruptions, Vulkaroth is a realm of shattered volcanoes, endless black deserts, and fields of jagged obsidian. Here, the ground quakes with every breath, and lightning dances unnaturally in the blood-red skies.
At its center rises Castle Magmathorne, a towering inferno-brick fortress built into the very maw of a supervolcano. Flames spew from its chimneys, and molten rivers form its moats. Inside, chaos reigns—
Primordial Jaune, draped in a sleeveless, spiked leather coat over charred armor, lounges on her throne of scorched bone and steel. Her eyes crackle like twin suns, and her aura radiates an oppressive heat.
When not battling her subordinates for sport, she rides across the wastelands on a beast forged from magma and bone, laying waste to wandering invaders or rogue demons that defy her domain.
To the east lies Nemereth, a land shrouded in perpetual dusk. The skies glow in sickly violet hues, and ghostly voices ride the winds. Dark, twisted forests filled with venomous plants and soul-stealing wisps stretch for miles, while corrupted lakes reflect not the sky, but hidden fears.
Castle Nyxveil rises from the heart of this cursed domain—an elegant yet unnerving structure of black marble veined with amethyst. Its halls are lit with soul-lanterns, and its walls are etched with living runes that whisper forgotten sins.
Primordial Violet, clad in a black military skirt uniform with her armband gleaming, rules from a throne of cursed crystal. Though she appears sweet, like a carefree princess, her smile is a mask. Behind it lies one of the most twisted minds in the Underworld.
In the west rests the ghostly land of Asphodelia. Snow-like ash drifts endlessly from the sky, covering the fields in a white shroud. Black roses bloom under dying trees, and silence dominates the land like a decree.
In the heart of this cold and desolate beauty stands Castle Ebonlace—a regal, fortress-like manor carved from obsidian and adorned with silver spires. Its great halls echo with the tapping of heels and the low murmurs of strategists and warlords.
Primordial Blanc sits upon her velvet throne, one leg crossed, her long white hair cascading like silk. Her crimson eyes scan the scrolls of politics, war, and demonic economy with a noblewoman's finesse. She is serene but lethal, like a blade hidden in satin.
The portal behind them shimmered shut, its arcane light fading into a ripple of silence. As the last trace of Varvatos' spell vanished, Rimuru Tempest stood still, absorbing the pulse of the Underworld.
Everything felt heavier.
The air was iron-thick, laced with the scent of brimstone and old blood. The sky—if it could be called that—seethed with churning colors like molten glass swirling under pressure. And beneath their feet, the ground was black, cracked obsidian veins glowing faintly with flowing, cursed energy.
Rimuru stepped forward and murmured, "So… this is the Underworld."
He took another breath, tasting the atmosphere. "Even the magicules feel twisted here. The air hums like it's alive."
Diablo—dressed in obsidian black with a dark red trim, his demonic aura cloaked behind refined elegance—smiled softly.
"Indeed, Rimuru-dono. This is where demons are born, broken, and made anew. A realm forged by carnage… ruled only by power."
Rimuru looked to him, studying his composed expression. "So this is your home?"
Diablo nodded, the flicker of nostalgia in his eyes. "Yes… though I do not serve it anymore." His eyes narrowed. "My loyalty lies with my Lord Varvatos. And now, with you—his chosen heir. The King of Nyvaris."
Rimuru glanced ahead. "So how do we find the Primordial Demons?"
"We don't," Diablo said with that familiar, dangerous smile. "We let them find us."
Rimuru raised a brow. "You're serious?"
Diablo's smile widened, and he gestured at the horizon. "Demons are drawn to power like moths to flame. If a being of overwhelming strength appears in the Underworld… they will come. Be it to challenge, to witness, or to submit."
Rimuru processed this and then gave a sly smile. "I see... then I guess I just have to be the flame."
Without another word, Rimuru closed his eyes. His body shimmered faintly as he unlocked a microscopic fraction of his true power—not a full release, merely a taste.
The effect was immediate.
The very world recoiled.
The earth screamed. The skies fractured. The crust cracked beneath his feet in a ring of burning light. Mountains in the distance shattered, and a wave of raw, incomprehensible pressure rippled out like a supernova of godly malice.
The Underworld, a realm forged to contain and embrace chaos, trembled.
Demons—hundreds of them—lurking in the hills, crawling in shadows, hiding in the cracks, were disintegrated on the spot. Those too close to the epicenter died instantly, their cores shattered like fragile glass. The remaining scattered like insects before a raging fire, fleeing in primal terror.
Even Diablo flinched.
He staggered half a step back, his arms instinctively rising as if shielding himself from the divine calamity. "T-This…" he stammered. "Even I… wasn't prepared for this level of power…"
Rimuru's eyes snapped open—glowing with cosmic threads of azure and gold—and with a soft breath, he retracted the aura. The chaos collapsed in on itself, and the world fell still.
The silence afterward was suffocating.
Diablo stood frozen, barely managing a nervous chuckle. "Rimuru-sama... that was... truly monstrous."
But then—he felt it.
He wasn't the only one.
The atmosphere suddenly shifted again.
Three presences—dark, ancient, demonic beyond measure—flared like comets approaching from different ends of the realm. Each carried an oppressive signature, overwhelming in their own right. Cold. Burning. Maddening.
Diablo straightened, eyes wide, voice low and hushed. "They're coming…" he said, almost in awe. "The Primordials… Blanc, Jaune, and Violet… they've felt your call."
Rimuru remained calm, though intrigued. "All three at once? Must've made quite the noise."
Diablo gave a smirk that didn't reach his eyes. "This is the Underworld, Rimuru-sama. When the lion roars... the other kings come to see if it bleeds."
The sky darkened.
From the north, a cyclone of cursed snow swept in, chilling the air around them to sub-zero. Black roses bloomed from the ground as a white figure emerged—a slow, graceful silhouette in a flowing dress of shadow and silk. Her aura was one of chilling elegance, like death delivered on porcelain wings.
Primordial Blanc, the Sovereign of Elegance and Terror, had arrived.
From the east, violet lightning tore across the sky, warping the very colors of reality. A mist spread, and with it came eerie laughter—playful, disturbing, utterly unstable. She floated in lazily, boots tapping the air, her long black hair trailing behind her.
Primordial Violet, the Sadistic Schemer, joined the scene.
And from the west… a shockwave.
The ground cracked, flames erupted, and a rumbling roar preceded the arrival of a fiery comet that crashed into the earth with godlike force. Standing in the crater, golden eyes glowing, was a woman wreathed in molten energy and smoke, arms crossed and grinning like a predator.
Primordial Jaune, the Blazing Berserker, stepped forward.
They all arrived without words, surrounding Rimuru and Diablo. They didn't acknowledge Rimuru at first.
Their eyes—each inhuman in their own way—locked on Diablo.
Blanc spoke first. Her voice was cold, dispassionate. "So… you return, Noir. Tail between your legs?"
Jaune scoffed. "Still playing errand boy for whoever snapped their fingers last?"
Violet giggled. "Oh~ little Noir still alive? I thought you'd been eaten by a god or something~"
Diablo's smile sharpened. He took one step forward, standing between them and Rimuru.
"I am no longer Noir."
The temperature seemed to spike. Or fall. Or twist.
"I was given a name… by my lord, Varvatos—the Sovereign of Oblivion, Master of All Abyssal Truths. I am now Diablo."
He met each of their eyes, unwavering.
"And you will use my name."
The Primordials paused.
Blanc's eyes narrowed. "Varvatos…? That name means nothing to me."
Jaune folded her arms, snorting. "Never heard of him."
Violet floated lazily, smirking. "Sounds made up. Like your fancy name."
Diablo's aura flickered dangerously. "Mock him again, and I will make you remember it. Etch it into your bones."
They grew still.
They felt it now. Diablo had changed.
This wasn't the same Noir that once played politics and war beneath the thrones of chaos. This was something elevated. Something dangerous.
Something... loyal to a greater force.