The multiverse theory, or the many-worlds interpretation, is a hypothesis, as yet unproven in physics, proposed by the American philosopher and psychologist William James in 1895.
—Beyond our own universe, other universes likely exist. These universes are a reflection of the possible states of the cosmos. Their fundamental physical constants may be identical to our own recognized universe, or they may differ.
In a 2003 paper on parallel universes, American cosmologist Max Tegmark divided the multiverse into four classes:
Level I: These universes share the same physical constants as our own but differ in the arrangement of particles. These universes can also be considered to exist in places beyond our known (observable) universe.
Level II: The physical laws of these universes are roughly the same as ours, but the fundamental physical constants are different.
Level III: According to quantum theory, an event can produce different outcomes, and all possible outcomes will form their own universe. Such universes can be classified as Level I or Level II parallel universes because the fundamental physical laws they follow are still the same as those of our own recognized universe.
Level IV is the mathematical universe hypothesis: The most fundamental physical laws of these universes are different from our own. Basically, up to Level IV, all possibly existing universes can be explained. Generally, the physical laws of these universes can be constructed using M-theory.
At this point, one must complain about the Nasuverse's practice of calling extragalactic space the "Outer Universe." A perfectly good Level I multiverse worldview was nerfed into oblivion.
According to the multiverse theory, the Campione! world would be considered a Level I multiverse, formed by the combination of countless worlds with similar fundamental rules.
---o---
In a world within the Campione! setting, on a worldline completely different from the one where the King of the End, Rama, resides, stood the Temple of Time in the domain of Persian mythology.
A man, robed in red that reached his feet and wearing a crown upon his brow, sat upon a throne, gazing into the distance.
His physique was powerful and robust, his chiseled face adorned with a beard.
He held a scepter—a golden staff symbolizing his royal authority—and his entire being radiated a brilliance like that of the sun.
His name was Mithra.
The God of Covenants and the Sun.
This is the mighty Mithra, the most powerful of all created beings, to whom I offer this libation.
In the Mihr Yasht, people revered him thus.
However, the current state of this god-king, once called the most powerful, seemed to be quite dire.
His dark brown hair was streaked with a considerable amount of white, and the dark circles under his eyes were heavy. Although his appearance was still that of a majestic man in his prime, his complexion was poor. If not for the kingly authority in his every move, he would have looked like a bedridden old man.
This king, who like Rama was entrusted with the mission of ending the Rakshasa who brought countless calamities upon the earth, carried out his duty of exterminating demon kings by raising the collective of divine armaments—the Divine Sword of Salvation—and slaughtering the Heretical Gods.
Clearly, wielding the Sword of Salvation for so long had pushed his body to its limit.
But even so, he still exuded a divine might so awesome it made one want to kneel.
The man, his majesty as vast as the ocean, stared straight ahead, waiting quietly.
And then—
A whirlwind stirred within the temple, bringing a slight smile to the virtuous king's face.
"Have you come, Son of Victory, who conquered the evil dragon Dahaka?"
The man, who involuntarily brought to mind concepts of royalty and the sun, sat upon his throne and greeted the distant figure with a deep, resonant voice.
"Was it you who summoned me?"
Responding to the king was a youth with a boyish face, dressed in a worn-out coat.
He stepped out of the whirlwind, smiling faintly. His handsome face radiated the unique aura of a hero's virtue, capable of captivating all people.
"Then I must offer you my thanks. It is only because you, who reside at the world's end, called to me that I was able to manifest and gain a physical body once more. Esteemed Mithra, the war god Verethragna offers you his gratitude."
"There is no need for thanks. I summoned you because I have need of you."
King Mithra nodded magnanimously, a note of approval in his voice.
"I thought you would have slept longer. You have arrived sooner than I expected."
"Then, great and holy king, for what purpose have you summoned me here?" the youth, who was slightly different from the war god of Rama's worldline, asked his monarch in a tone that was neither servile nor overbearing.
Possessing the Sword of Wisdom, he naturally had extraordinary powers of observation and judgment. The holy king who had summoned him was an existence like the sun, but for some unknown reason, this sun had become a setting sun, nearing the horizon.
"Could it be that a demon king is running rampant in this world?"
The summoned war god was more than willing to resolve the worries of another world's monarch.
"In the world I rule, the conditions for the birth of a child of folly do not exist," the king, who shouldered the destiny of annihilating demon kings, stated plainly. Unlike Rama, that master of slacking, Mithra adhered to the principle of "if all the Heretical Gods are dead, no God-Slayers will be born," and had gone through and cut down every Heretical God who had descended upon the mortal realm, one by one.
"Then, what do you mean?"
Though he possessed wisdom beyond reason, the information he had was too limited. Verethragna, momentarily confused, looked at Mithra, waiting for his reply.
"However, it is only my world that is free of these fools."
The god-king, whose lifespan had already been burned away, had a coldness in his eyes that seemed capable of freezing time and space. He waved his hand, and a greatsword immediately materialized before Verethragna.
The greatsword was thrust into the stone floor. Its platinum-gold blade was incredibly thick, shaped similarly to a hatchet. The blade was unusually tall and the entire weapon shimmered with a platinum-gold light.
"This must be the Divine Sword of Salvation," Verethragna murmured in astonishment, looking at the divine sword that bore the shadows of all the gods' weapons.
His tone was unbefitting of the wise God of Victory. But it was no wonder. The scene before him was enough to make even a war god like him gasp in genuine awe.
"So you are this world's King Who Manifests at the End."
"I am the god who was granted the Divine Sword of Salvation by the god of fate, to become the hero who annihilates the demon kings," Mithra confirmed with a nod.
"But if you are the King of the End, your power is sufficient to defeat any enemy. Why would you require my assistance?" Verethragna asked, his gaze sharp as he stared at the man seated upon the throne, having clearly sensed that something was amiss.
"You should be able to sense it vaguely, can you not? This body of mine can no longer take to the battlefield. I am no longer a warrior worthy of the Sword of Salvation."
"Indeed. To fulfill the mission of annihilating the demon kings, I have swung this Divine Sword of Salvation countless times, erasing the demon kings and the very elements of their birth. This is the price."
The King of the End, Mithra, confessed to his brutal slaughter of his own kind. For a moment, his eyes, so full of virtuous authority, flashed with a crazed and stubborn light.
"To strangle all crises in the cradle?"
"Such admirable valor and determination," Verethragna chuckled in a low voice. As a war god, he saw no issue with slaughtering one's own kin.
"My body completely collapsed four hundred years ago."
Beside the jade throne where Mithra sat, an aberrant god materialized.
"The reason I can sit here and speak with you is because it has helped me pause my time."
It was a "mask."
A stone mask, floating in the air.
Carved upon it was the magnificent face and mane of a lion. A living snake grew from each of its two ends, their tongues hissing and flicking.
It was Zurvan, the god of time worshipped by the Zurvanism sect of Zoroastrianism, the secret god who presided over eternity and infinity, the creator of light and darkness.
If it was him, he was indeed capable of halting the time of a god.
"Then why did you, who rules a world without Rakshasa, need to summon me here?"
Upon arriving at the Temple of Time, the war god had vaguely smelled an aura that was a mixture of god and Rakshasa. A cruel, murderous intent flashed across his face.
"Am I to understand that an existence similar to a Rakshasa has appeared in this world and needs to be cleansed?"
The handsome youth bowed to the man seated on the throne.
"If that is the case, I am willing to act on your behalf."
"No... I will go to battle myself."
As if sensing a great crisis was about to unfold, the monarch, who would absolutely not permit the aura of a Rakshasa to exist within his domain of perception, spoke slowly.
Go to battle... himself?
As if hearing something very strange, Verethragna looked at the king, who might perish the moment he stepped outside the temple where his time was frozen, his expression one of shock.
"I need only wait for Zurvan to create a portable barrier."
The monarch, whose divine lifespan had been completely exhausted, gazed into the distance at another land that, for some unknown reason, had connected to his own world.
The Child of the Sage, possessing the divinity and authorities of multiple gods but not adhering to any divine office, was flaunting his power with the impunity of a Heretical God.
That world may well be the place of my demise.
After all, that was a monster who had grown up under the doting love of Prometheus.
The god-king, knowing full well that a Child of Prometheus and a Child of Epimetheus were two entirely different concepts, stood up, an unprecedented madness in his eyes.
But so what?
Those who bring chaos to the world, be they Rakshasa or Heretical Gods, must die! The Child of the Sage would be no exception!!
"Verethragna, this campaign carries the risk of my demise," the ancient god-king said, his voice impassive as he looked at the divine sword thrust into the stone floor.
"If I should fall in battle, you are to take up this sword, succeed me as the King Who Manifests at the End, and continue the hunt!"
Author's note: ps: I'm suddenly feeling that Mithra's character is so righteous and noble...