Orochimaru
Orochimaru couldn't help but lick his lips in anticipation.
Today will be the day when he finally achieves a monumental breakthrough and reaches the first significant milestone in his pursuit of immortality and amassment of all knowledge.
With a snap of his fingers, one of his subordinates entered the dimly lit chamber, carefully placing a small, lifeless body of a young boy at the center of the room.
Orochimaru approached it soundlessly, his pale fingers reaching out to brush against its hand. The skin was smooth, fair and delicate. Only a shade darker than his own, that looked as if devoid of blood. A result of the harvested cells from captured Uchiha specimen, that would grant this form a more human appearance.
It took many attempts to make it stable, no matter how many or who's cells he had stolen from that particular clan, they always rejected his own, as if disgusted by the very notion of union. As if his blood wasn't noble enough for them.
Until now, that is.
A perfect vessel. A beautiful effigy.
With a swift flick of his kunai, he sliced its wrist open, drawing fresh blood to inscribe the necessary summoning seal. As his fingers blurred through the intricate sequence of hand seals, he felt a fraction of his chakra siphon away; now forever gone. Such was the price to summon a soul from the Pure Land and bind it to the mortal plane. To steal from the heavens themselves.
This technique, however, differed from the one created by the Second Hokage. His version relied on the law of equal chakra exchange to bind the soul to the body, preventing it from fragmenting into paper, while retaining its mortality.
Unfortunately it did not bind the summoned soul to the caster's will, which was an unacceptable flaw in Orochimaru's eyes.
Still, possibilities of this technique were limitless. If refined, if mastered, it could even allow him to resurrect himself indefinitely.
A brilliant blue light erupted from the ceiling, piercing through the darkness and bathing the body in an ethereal glow. Orochimaru's breath hitched as the soul descended, but instead of the expected small wisp of blue color, a full-bodied silhouette appeared, its translucent form eerily defined.
A man. Long hair tied in a ponytail.
Orochimaru frowned. 'It shouldn't be like this.'
As the soul settled into the corpse, the very air in the chamber shifted. The warm, divine glow flickered and was replaced by a suffocating chill; a cold so sharp and unnatural it rivaled the mountain peaks of the Land of Snow.
The body began to rise, floating within the shroud. It began glowing, twisting and squirming as the soul tried to adjust itself into its new form.
And then, just as suddenly as it had begun, the glow vanished and so did Snake Sannin's adroit little smile.
In its place, blood poured forth from every orifice of the small body; eyes, ears, nose, mouth, even the anus. The expression, once vacant, twisted into something horrifying; a visage of excruciating pain. A gurgled howl tore from its throat, drowning in the crimson flooding its lungs.
As the light fully disappeared, darkening the whole room; the feeling of dread only deepened, it entangled Orochimaru in a tight embrace, under which any lesser man's legs would have buckled.
But Orochimaru merely exhaled, unfazed and unshaken. If anything, the spectacle only heightened his determination.
He formed a seal, channeling chakra through his body. The oppressive force resisted, clinging to him like a desperate mother pulling a child away from danger.
"How foolish."
With a flick of his fingers, the Rat seal formed.
This failure was not due to an excess of chakra; he had been meticulous in ensuring that only a small portion of his reserve was sacrificed. No, the issue lay with the soul itself, the Sage deduced.
'It is too whole, too resistant to change. It had never truly reached the Pure Land.' He scowled, his expression thoughtful.
Right now, the soul tries to reshape the body, which will undoubtedly fail. It was not Edo Tensei after all, still it held far greater potential than Nidaime's infamous jutsu.
Orochimaru blinked, clearing his mind from irrelevant thoughts. Soul was at fault here, so he was going to trim it.
There would be consequences, of course. Memory loss, fractured identity, perhaps even emotional instability. But all of that was preferable to losing the vessel he had so carefully cultivated. With luck, it might even make the subject more pliable.
Another seal followed. The blood-drenched corpse fell silent, frozen mid-scream, its lifeless eyes wide with terror. The pulse of Orochimaru's chakra surged through the complex seal on the floor.
Time seemed to freeze as the inhabited corpse stared agape with its bloody eyes into the ruthless visage of Snake Sage himself.
Orochimaru felt a pulse of his chakra run from the seal through the struggling body as he finished the last hand sign. It cut away chunks of soul that he deemed least important. He could feel it wrestle against his grasp with renewed fervor, trying to scream at him to stop, that it hurts; but all that left its mouth was a breathless wheeze.
Blue chunks of light shattered into smithereens and finally Orochimaru felt himself relax, as thousand little pieces of blue enrgy started to float towards the ceiling. He released his hold onto the seal and watched completely entangled as his newest addition whimpered and squealed in fright when its fingers passed through the fragments of the soul. It could only stare longingly as they floated upwards in lulling motion.
It felt like watching a painting come to life before his eyes. Evoking feelings and emotions unaccountable to the human heart. Closest description Orochimaru could think of, would be that of a nostalgic yearning for something lost, that you never had in the first place.
Then the subject's swollen, tear-streaked eyes met his again.
Confusion, fear. panic.
And finally: realization.
Orochimaru's grin widened.
It was an utter success.
In an instant, silence fled the room as Orochimaru's raspy laughter filled its place.
'What an exquisite performance...'
The child's terror-stricken gaze remained locked onto his own, and Orochimaru knew it was time.
With a single hand seal, a simple genjutsu, the child collapsed, unconscious before it even hit the floor.
He stepped closer, crouching beside the newly born entity. His fingers traced the child's bloodied cheek as he murmured:
"From now on, your name shall be Kentarō..."
A fitting name for one of his own blood. His firstborn.
"…and my future vessel."