Light blinded them—cold, not warm. Not the glow of illumination, but the flash of something ancient and watching.
Kaito hit the stone floor with a grunt, his hand still clutching his Duel Disk. His vision slowly returned, and he saw the others scattered across a vast chamber that looked nothing like the rest of the Obsidian Tower.
The walls pulsed with black veins of magic. Enormous statues of ancient Duel Monsters loomed from each corner—Zera the Mant, Serpent Night Dragon, Black Skull Dragon, and something unrecognizable: a skeletal dragon cloaked in chains.
Alexis coughed beside him, rising to her knees. "Where… are we?"
Jaden pulled himself up, looking around with widened eyes. "This place… it feels like it's alive."
Bastion examined the floor. It wasn't stone—it was a single massive card. Inscribed into the chamber's center was a circular platform with runes and a locked pedestal.
Kaito stepped forward. "This is the heart of the Tower. And that…" he pointed to the pedestal, "is the source of the energy I've been feeling."
Hovering above it was a Duel Monsters card—but this one shimmered with unstable energy, as if resisting being seen. The card's text blurred and shifted when anyone tried to read it.
"Is that a spirit card?" Alexis asked.
"No," Kaito said grimly. "It's more than that."
Suddenly, a voice echoed through the chamber.
"You have passed the trials. But the final key remains."
From the shadows emerged a new Harbinger—this one cloaked in obsidian armor, his face hidden beneath a dragon-shaped helm. Unlike the others, his Duel Disk wasn't activated yet.
"You are the inheritors of the Duel Spirit Realm's future," he intoned. "But you are also the keepers of its greatest sin."
He gestured to the card. "That deck—The Forbidden Deck—was sealed a millennium ago. Its power eclipsed all others. It consumed spirits and twisted the will of its users. One man once wielded it, and nearly shattered the barrier between the human world and the Duel Spirit realm."
Jaden's expression darkened. "Why bring us here then? If it's that dangerous—why show us at all?"
"Because it will be unsealed," the Harbinger said. "Whether by your hand or another's."
Kaito stepped forward, locking eyes with him. "What are you?"
The Harbinger removed his helmet—and revealed a face eerily familiar.
Kaito staggered back. It was his own face.
"You… you're me?"
"A fragment," the being said calmly. "Born from the duel energy you've repressed. The rage, the instinct, the fear of failing again. I was created when you died in your previous life… and when you were reborn, I was left behind in the Spirit World."
Kaito clenched his fists. "So you're a shadow of who I used to be."
"No," the echo replied. "I am what you might become… if you claim the Forbidden Deck."
Jaden stepped between them. "We're not going to let that happen. Kaito's already proven himself stronger than his past."
"Then duel me," the shadow said. "Here and now. If you defeat me, I'll relinquish the deck's seal. But if I win…" his voice dropped, "I claim your soul—and your future."
Kaito didn't hesitate. "Fine. Let's settle this."
They stepped onto the duel platform. Runes activated beneath their feet, and the chamber darkened to a swirling twilight.
Kaito - 4000 LP
Echo-Kaito - 4000 LP
Echo-Kaito began with a Field Spell: Dragon's Maw, altering the field so that all Dragon-Type monsters gained 500 ATK but couldn't be tributed.
Then he summoned Vileborn Dragon (1700 ATK), and set two cards.
Kaito took a breath, then summoned White Stone of Ancients, activating Return of the Dragon Lords to Special Summon Blue-Eyes White Dragon from his hand.
The arena erupted in white flame as his signature dragon appeared, roaring across the field.
He launched his attack—White Lightning tore through Vileborn Dragon, dropping Echo-Kaito's LP to 3000.
But Echo-Kaito grinned.
"You activated my trap: Dragon's Mirror Reversal."
The destroyed Vileborn Dragon fused with energy from the graveyard, summoning Corrupt White Nova Dragon (3000 ATK)—a shadowed, skeletal version of Blue-Eyes, with red lightning for wings.
The duel escalated. Kaito brought out Blue-Eyes Spirit Dragon to lock down effects, then combined it with Azure-Eyes Silver Dragon. He fought methodically, defending against Echo-Kaito's relentless waves of corrupted dragons.
Finally, Kaito drew his last card.
Burst Stream of Destruction.
With no monsters on Echo's side for protection, and his own Blue-Eyes Alternative White Dragon on the field, Kaito activated the spell—wiping out the final defenses.
Then he attacked directly, bringing Echo-Kaito's LP to zero.
The shadow staggered backward, his form breaking apart into particles of light.
"Well done… you've passed the final test…"
As the light faded, the Forbidden Deck stabilized—still sealed, but no longer hostile.
Jaden approached. "So… what now? Do we use it?"
"No," Kaito said, staring at the deck. "Not unless we absolutely have to."
Alexis stepped beside him. "Then let's make sure it never comes to that."
Behind them, the runes of the chamber lit up in approval. The path back to the surface opened.
But far away, across the sea, a cloaked figure stood before a massive gate inscribed with ancient Duel Spirit markings. He raised a hand—and three sigils glowed in response.
"The deck is awake," he murmured. "Now let us begin the final arcana."