Though it was called Ea, this was merely a nickname of convenience he had given it.
In fact, it might not even be a sword at all.
After all, this was something that had existed long before swords and spears had appeared in history.
It hailed from an era more ancient than humans, older than even the planet itself.
It was a rarity among rarities, a pure manifestation of the power wielded by gods to enact Genesis.
It was the beginning of all on this planet. It was that which clove apart Heaven and Earth.
It rent the void and created the sky, then pierced the sky and returned it to the void.
This power symbolized the Beginning and the End, and only Gilgamesh, who inherited the essence of the gods, was permitted to wield it.
Therefore, when Gilgamesh swung the sword with all his might, it was defined as...

Anti-world Noble Phantasm.

Offensive Noble Phantasms were classified into tiers such as anti-personnel, anti-army, anti-fortress, and so forth.
In many cases, an anti-personnel Noble Phantasm was more appropriate to a one-on-one battle between Heroic Spirits than an anti-army or anti-fortress Noble Phantasm. But when it came to the sheer power of an anti-world Noble Phantasm, considerations such as compatibility and applicability went out the window.
It was absolute power — the power to destroy the World itself.
Regardless of whether the opponent was an individual or a group, it simply broke the world they existed in.
Such was the attack which Gilgamesh unleashed with all of his strength.

Against a single Heroic Spirit, Gilgamesh attacked without hesitation. This was neither play nor negligence. The King of Heroes discarded his usual arrogance and put everything he had into a single attack.
On the ground stood the Heroic Spirit Enkidu.
This attack was a message to his oldest, only friend. It was a song of pure joy for their reunion, conveying everything he felt as a king, as a hero, and as the man Gilgamesh.

“O Ea, sing to thy heart’s content.”

Gilgamesh spoke these words not to the Heroic Spirit below him, but to the sword in his hand.
As if in response, the cylindrical sword twisted the air while spinning like a tunneling drill. The whirlwind grew and drew in even more air, and a small tornado formed.
The two cyclones combined and created an even greater distortion in the air — all of this was drawn and compressed in the sword.
The layers of wind grew even denser and exceeded the physical laws, quickly turning into a lethal weapon that ripped apart all of Creation, and began condensing into a fissure in space itself.
Sound and light converged in the distortion, and silence and darkness encircled the sword. As if to excite the howls of the seemingly living weapon, Gilgamesh gripped it even more strongly, and swung it down at his long-lost friend without hesitation—

“ENUMA ELISH
Star of Genesis — Separate Heaven and Earth!!!”

The distortion ruptured.

The entire universe that had been compressed beyond limit focused around Ea, and was released by its wielder’s slash. The resulting pressure wave sundered the nearby space. The World itself was sucked up by the chasm of the Void, and turned inside out.
Who would believe that this scene was caused by the swing of a sword?
The Void emerged from the chasm, rupturing space further. The World eroded, giving way to countless fissures in reality.
The sands cracked like clay. The sky and clouds were shredded like so much paper.
It was a hellish landscape, as if a painting of the desert had been thrown into a blender.
The “slash” of the sword twisted and tore the planet, sending a wave of destruction at the Heroic Spirit standing on the ground.

Then, Enkidu…

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Enkidu’s manifestation as a Lancer
spear-wielding Heroic Spirit was probably due to his Noble Phantasm.
However, it was not quite accurate to call it a Noble Phantasm.
It was a Chisel to tie the bond between gods and men. This was Enkidu’s true nature.
According to one tale, in an attempt to cling to their power, the gods had placed Gilgamesh upon the earth as a chisel to ensure that humans would continue to worship the gods as gods.
However, he did not fulfill that duty, instead reigning in such a way to personally drive humanity away from the gods. Perhaps the King of Heroes had forgotten his charge, or perhaps he simply ignored it.
A spear was made to question, investigate and discipline the King of Heroes, who had failed in his duty. Namely, Enkidu was born as the concept of a god-forged weapon to pierce Gilgamesh’s hostility and return the Chisel to the gods’ own hands. Thus, the likelihood was high that he was chosen by the Holy Grail for the Lancer class.
It could also be said that his Noble Phantasm — an attack that used his own body as a weapon — was best personified by a Lancer
spear wielder.
He would simply puncture the World and stitch it back together.
If a wall existed in the chasm between Heaven and Earth, he existed to pierce that concept.

In the instant that an attack to destroy Eternity drew near—
The planet sang.

A gigantic amount of mana gushed forth at Enkidu’s feet, and moved to swallow Enuma Elish
the Star of Genesis Separating Heaven and Earth head-on.
“Don’t hold back.”
Those words were not directed at the Heroic Spirit he was facing.
As the King of Heroes had spoken to Ea, so too did Enkidu speak to the massive mana engulfing the Void cracks in space. He spoke directly to the planet.
“I am a weapon. Wield me as you please.”
Instantly, enough mana surged forth to make the earlier flow seem like a mere trickle. Several times more mana geysered from the earth’s surface, becoming a cyclone of energy enveloping Enkidu’s body.
Then, the energy became a titanic lance of light to pierce Heaven and Earth, with the Heroic Spirit as its core.

It was a concept that once propagated life.

It was the fiery coals that had been used to overcome mankind’s first fears.

It had walked alongside mankind through hell, and now, it sang of Paradise.

The Separation of Heaven and Earth was of little consequence.

From the past to the future. From the future to eternity.

It would link the land and sea to the heavens.

Terror was etched in the karmic endeavor of Life. Thus, with time humanity would rewrite it down to its genes.

Both a weapon and a tool, a mud doll without form.

Walking among humans, it, who had acquired the joy of friendship, shouted.

As this world was already Hell, humanity would create Paradise on its own, and comprehend the Beginning.

Enuma Elish
O Humanity, Bind Thy Gods!!!

Whilst destruction had been loosed upon the earth, a mighty strike hurtled toward the sky.

Enkidu
The Chisel of the Gods stitched the sundered World anew as it drove a straight line at its target, meeting the world-tearing Sword of Rupture in a violent clash.

Reality — desert region

Power and power.
Noble Phantasm and Noble Phantasm.
Divinity and weaponry.
When the two extremes crashed into each other, the spatial distortion blasted the surroundings asunder.
In the interstice between the two attacks, an immense struggle of energies commenced.
In the distant past, the Sacred Prostitute watched the heroes clash from the ancient city of Uruk, speaking these words in a daze:
“I felt as if the World was born seven times, and destroyed seven times.”
In the midst of such swirling power, the two Heroic Spirits never ceased smiling.
It was not as if they could spare a moment to laugh. If either one let his guard down for even a moment, his body would be rendered unto oblivion. Both of them knew that.
Nonetheless, it was but a trivial matter. To these two, this was mere child’s play. A childish contest of wits.
Still, neither could afford to restrain himself nor give the other any ground.
They only wanted to compare their powers. They wanted to struggle, and bash fist against fist.
That they were technically enemies in the Holy Grail War was little more than happenstance. It simply the fastest way for each to feel for himself that his friend was there.
Their friendly battle just happened to involve everything around them.
Besides, the energies of the two Noble Phantasms cancelled each other out, and dispersed into the surroundings.
Though, this “dispersion” left tornadoes that ripped and tore their way into the surrounding landscape.