As they left the hospital, Reed paused, lips pursed, before turning to Sebastian. "This world's far more complex than I ever imagined, Sebastian. Current science can't reveal its true essence. But I'm not giving up. One day, I'll uncover its secrets through scientific discovery."

Sebastian gave a thoughtful smile. "Science and magic are parallel paths, Reed, each leading to the world's deepest truths. Magic is a deeply personal pursuit, whereas science thrives on collective endeavor. I wish you success in your journey."

"I'm determined to succeed!" Reed said, his voice firm with resolve.

Sebastian nodded. "By the way, you're heading to space soon for research, aren't you?"

"Yes," Reed replied, enthusiasm brightening his face. "My three friends and I, four astronauts, will test theories and run experiments. When I return, I'll bring back valuable insights."

Sebastian's smile turned knowing. "I'm certain you'll gain far more than you expect from this mission," he said, a hint of foresight in his tone. He'd long suspected Reed's identity, and Victor's too, after their time together. Their presence confirmed this world was fundamentally distinct from the one he'd known. His journey to the X-Men's parallel world, sparked by the Space Stone, had altered its course, creating a new universe with branches stemming from his actions, destined for a unique end.

When Reed's car arrived, Sebastian waved him off, then walked away, his mind heavy.

A week later, he learned Victor had vanished from the hospital at midnight, his destination a mystery. Sebastian sighed softly, feeling both regret and respect for his friend's choice.

-------------------------------

In the dimly lit basement laboratory of his modest villa, Sebastian sat before his computer, watching the live broadcast of Reed Richards and his team's spacecraft soaring into the cosmos. As the stream concluded, he switched off the computer, the screen fading to black, and lingered at his desk, lost in thought for the first time in ages, his mind heavy with Victor's absence and the shifting world around him.

After a quiet pause in the stillness of his lab, Sebastian reached into his pocket and drew out a dark red gem, the Reality Stone, one of the six Infinity Gems, its faint glow casting eerie shadows across the room.

He gazed at the Reality Stone in his hand, its power thrumming softly, and cast aside all hesitation, resolve firm in his heart. Stepping back to clear a space, he prepared to attempt Animagus transformation for the first time in this laboratory, a spell he'd long struggled to master in this altered reality.

In this world, the magic Sebastian had known from his previous life had undergone significant shifts, molded by the unique rules of this universe. The more advanced the spell, the greater its divergence from what he'd once known. Animagus, a pinnacle of transfiguration magic, had changed so profoundly that his past attempts had ended in failure, each effort meeting a frustrating dead end.

He had realized then that mastering Animagus here required him to find his own path, to navigate uncharted magical terrain. Until he acquired the Reality Stone, he'd found no way forward, no method to bridge the gap. Now, its power offered a spark of possibility, a chance to unlock this elusive art.

Sebastian settled cross-legged on the cold floor, clutching the Reality Stone in both hands, its energy pulsing against his palms. He closed his eyes, centering himself, and began to chant the incantation with quiet focus, each word resonating with intent.

"Animago, Animaudium, Animago, Animagus!"

Suddenly Reality Stone pulsed, releasing black and red ether particles that swirled like mist, seeping into Sebastian's body through his hands, their eerie glow illuminating the basement laboratory.

Sebastian's heart raced as he felt profound alterations sweep through him. His body began to shrink, compacting with an unnatural grace, while sleek black feathers sprouted across his skin, each glinting faintly in the Stone's light.

In his previous life, his Animagus and Patronus had both been Ravens —his Patronus a radiant silver-white, his Animagus a striking black crow with piercing golden pupils. As his form dwindled and feathers emerged, Sebastian remained calm, his confidence unshaken by the familiar process, maintaining the spell's flow while awaiting its completion.

But an unexpected disturbance disrupted the spell's flow. Thick black smoke billowed from Sebastian's transforming body, warping the crow shape he'd begun to assume. His form dissolved into a chaotic swarm of black particles, spiraling around the Reality Stone in a frenzied dance, the laboratory's air humming with raw power.

He couldn't tell how much time had elapsed in that fleeting moment, whether seconds or hours, but the particles abruptly converged, coalescing into a crow with golden pupils that gleamed like molten metal. Wisps of black smoke clung to its form, its wings trembling slightly as it hovered in the air, a creature born anew.

Sebastian, now the Death Raven, inspected his Animagus form with a mix of awe and curiosity. Outwardly, it mirrored the crow of his past life, but its inner essence was remarkable, transformed by forces beyond mere magic. The Reality Stone had woven four extraordinary forms into his being, each embodying a distinct power.

In Phase Form, Sebastian could glide through material barriers, moving through the void unscathed. Only attacks targeting the soul or wielding divine authority could harm him, ensuring his safety in this ethereal state.

In Split Form, his mental strength determined the number of duplicates he could summon. As long as one survived, he could regenerate instantly, though each destroyed duplicate drained a portion of his power, a costly but potent ability.

In Phantom Form, his body could grow immense, his strength and abilities scaling with his size. The larger he became, the greater his might, a towering force limited only by his endurance.

In Death-Telling Form, he became an apostle of death, guiding spirits to the realm of the dead, a solemn role that resonated with the Reality Stone's dominion over existence.

Sebastian marveled at these powers, understanding their emergence stemmed not only from the altered Animagus spell but also from the Reality Stone's significant influence.

He reflected on Wanda and Pietro, altered in this world yet empowered by the Mind Stone in another reality, granting them extraordinary abilities. Similarly, the Space Stone had imbued Captain Marvel, Carol Danvers, with strength enough to challenge Thanos head-on.

The Infinity Stones, when wielded with precision, could bestow unparalleled power. Sebastian's use of the Reality Stone to reshape Animagus magic, absorbing a fragment of its essence, had naturally granted him these formidable abilities.

In Phase Form, Sebastian spread his wings, his body dissolving into wisps of black smoke, resembling a spectral raven. He glided effortlessly through the laboratory's walls, instruments, and ceiling, unscathed by material barriers, his ethereal state impervious to physical harm. Only attacks targeting the soul or bearing divine authority could threaten him, a safeguard that filled him with quiet confidence.

Gazing at his villa below, its silhouette sharp in the moonlight, he soared upward, passing through the roof to ascend into the night sky.

Transitioning to Split Form, Sebastian's form shattered into dozens of identical ravens, each a fragment of his consciousness, their number tied to his mental fortitude. As long as one survived, he could regenerate instantly, though each lost duplicate drained a portion of his power, a costly trade for such resilience. The sudden fragmentation overwhelmed him, his mind struggling to adjust to the myriad perspectives. Several ravens collided in the clouds, forcing him to merge them swiftly.

At thirty-two duplicates, he found balance, realizing that summoning more wasn't always beneficial, provided they stayed within a controllable range.

With a surge of will, Sebastian shifted to Phantom Form, the thirty-two ravens coalescing into a single, colossal bird, its wingspan rivaling a passenger plane. His strength and abilities amplified with his size, a towering force limited only by his endurance. A powerful wingbeat unleashed a sonic boom, scattering the clouds below like ripples on a stormy sea. Testing his claws, Sebastian sensed their might, capable of tearing through steel with ease, his heart pounding with the thrill of such raw power.

The final form beckoned—Death-Telling. Shrinking to a sleek raven, Sebastian embraced his role as an apostle of death, guiding spirits to the afterlife, Black smoke billowed from his body, laced with faint red lightning, accompanied by ghostly wails that chilled the air. His vision faded to black, gray, and white, the world cloaked in an eerie pallor.

A blurred phantom appeared—a woman in black, her words muffled, her presence heavy with portent.

(A/N: Guess who?)

Before he could grasp her message, a deep primal dread erupted from his soul, shaking him to his core.

The Animagus form collapsed, reverting him to human shape as he plummeted from the sky, the wind howling past. The dread stifled his magic, rendering spells impossible, his wand inert in his trembling hand.

As the ground loomed closer, Sebastian clenched his jaw, forcing his magic to stir. At the last second, a vortex of twisted space swallowed him, depositing him in his underground laboratory, where he collapsed, gasping for breath.

That same primal dread had seized him in Death-Telling Form, a terror he'd last felt when contemplating the Killing Curse long ago.

This was also the main read when in dire situations, he didn't try to use the Killing curse, because he always feel the same dread just like he felt now.