Like many areas in the region, natural hot springs flowed out of the ground and gathered in the valley.
But here, the water was thick with iron, staining it deep red.
Because of the heat and the way the valley trapped air, foul-smelling steam hung permanently above it, choking every breath.
Life avoided the place.
No animals lived there, and only a few patches of twisted vegetation managed to survive on the rocks.
This desolation had become home to the exiled Chinoike clan.
Down below, the clan was tearing itself apart.
Screams echoed through the mist as members slaughtered one another beneath crude, blood-painted symbols covering the ground.
Yin and Yang essence swirled invisibly in the air, thick and unbalanced, like something alive.
But instead of truly feeding into the ritual chalice placed before the apparent leader of one warring faction on the surface, the energy slipped away unnoticed.
To the people above, it was invisible, just another shimmer in the heat, another flicker in the crimson haze.
Yet beneath the earth, it moved with purpose.
The essence sank deeper and deeper, threading through layers of scorched soil and blackened rock, drawn toward something hidden far below.
At the bottom of that cursed valley waited a sealed chamber, silent and forgotten, where the stolen power gathered and began to breathe.
Inside that chamber rested a strange coffin.
Within it lay a perfectly preserved corpse of a man.
His long brown hair had been cut short on top, with two bandaged locks framing his face.
His eyebrows were trimmed, a mark of old nobility, and his dark eyes rested closed.
He wore a light kimono fastened by a dark sash, magatama beads lining its collar, and a black bodysuit underneath.
Yet something was wrong. Black marks, like tangled roots or veins, spread all over his skin.
They pulsed faintly, as if alive, coiling beneath the flesh.
The corpse began to stir, slowly at first, then more violently, as the twisted ritual above reached its peak.
The air trembled. The steam thickened. The valley seemed to hold its breath.
It wasn't just about reviving the perfectly preserved corpse; it was about giving it a new master.
Black Zetsu himself.
Months earlier, he had finally managed to somehow break away from the recently revived Madara Uchiha.
The moment he escaped, he came here, to one of the secret bases he had built long ago beneath this valley.
It was one of the many contingencies he had prepared over centuries of waiting for his mother's return.
Now, he was attempting something far greater than simple survival.
This hidden chamber was where he had brought the preserved body of Indra Ōtsutsuki, using ancient methods lost to all but himself.
His goal was to claim it completely, to inhabit Indra's body and make it his own.
His current form was unstable, hardly a true body at all, incapable of performing normal ninjutsu, among other deficiencies. Truly useless against top tiers that were on guard against his parasitic attack.
But to regain control of the world's path, to reclaim the Rinnegan and the Demonic Statue, he needed this vessel.
Only through this powerful Indra's body could he begin steering the world once again.
Long before the shinobi nations, when Hagoromo still walked the earth, Black Zetsu began whispering into Indra's ear.
He had found the elder son easier to reach, his pride already wounded by being denied succession.
Zetsu didn't force him; he didn't have to.
He only spoke the right words at the right times, feeding the growing fire of resentment inside him.
He told Indra that Hagoromo had betrayed him, that strength was meant to rule, that love without order would only lead to ruin.
The seed took root quickly. What followed was not possession, but a slow weaving of thought and will.
Every choice Indra made, every technique he created, carried a faint trace of Zetsu's intent.
Exhausted by his endless battles with Asura, most ending in bitter defeat, and the unending wars waged by their followers, he barely survived the final clash, only to succumb to his wounds some time later.
However, the blood of the Ōtsutsuki refused to easily rot.
His followers sealed his remains in a hidden shrine far to the east, believing he would one day return. Zetsu made sure of that.
Over the ages, he kept watch from the shadows, occasionally restoring the seals with his own chakra, keeping the corpse preserved.
No one ever knew it wasn't devotion, it was maintenance.
He had been guarding a potential vessel for the future. Indra's purpose, in Zetsu's eyes, was not yet complete.
Meanwhile, Indra's soul continued to reincarnate alongside his brother Asura, an endless cycle that became the cornerstone of all Black Zetsu's plans.
Only through the merging of those two halves, sometime in the future, could the Rinnegan awaken, the Demonic Statue be summoned, the tailed beasts be gathered, and his mother's resurrection be achieved.
Zetsu believed this cycle existed because both brothers still carried traces of Ōtsutsuki blood. Their souls were also too powerful to pass completely peacefully into the Pure Land.
The resentment between them had also perhaps grown so vast and ingrained that it transcended mortality itself, becoming a spiritual curse.
That festering grudge kept regenerating, lifetime after lifetime.
However, not every reincarnate truly embodied Indra's or Asura's essence.
Most were pale imitations, shadows carrying only fragments of their will.
It wasn't until Madara and Hashirama were born that the cycle produced near-perfect successors.
Their balance of power and conviction was unlike any before, and that was why Black Zetsu's true plan could only begin in this era.
The reason Black Zetsu had waited so long for a "new" Indra, like Madara, to appear and awaken the Rinnegan, rather than using Indra's original body, was simple: there had been no Hashirama until recently.
Without both perfect, or at least near-perfect, halves of Hagoromo's blood existing in the same era, the plan could never move forward.
Yet even when Hashirama finally appeared, Zetsu avoided using Indra's body, instead opting to use the tricky Madara Uchiha.
In truth, he had always been wary of this scenario of "entering" the old Indra.
Because, even now, he didn't fully understand what might happen once he did.
The body was an empty vessel, devoid of a soul, yet its genetic essence remained perfectly intact, and essence could shape the soul itself to an extent.
So, if Zetsu were to merge with it, would he still be himself, or would something entirely new emerge from the fusion?
But, he no longer had the luxury of hesitation.
The world was rapidly slipping completely beyond his control.
Madara was gone, the pieces scattered, and every delay risked losing everything.
If he wanted to steer the course of fate again, he needed to act now, no matter the cost.
Indra's body, even as a vessel, was not weak.
His perfect, 'demi-god', highest possible version of the Eternal Mangekyō Sharingan still rested within, and the ongoing ritual would refine this form even further, merging Yin and Yang in unnatural harmony.
Zetsu believed that once he took over, his power might even surpass Indra's peak.
And with such strength, why not begin by removing obstacles close to him?
His first thought was of the "neighbor" to the south, the one whose existence had begun twisting the balance again. Ryusei Senju.
Zetsu's grin deepened in the dark.
Once he awoke, perhaps that Senju would make a fine first offering for his new Yin-Yang ritual ascension.