Joyless Slaughter was Total Concentration Selfless Breathing's transformation that Kai rarely used because of its sheer scale and complexity.
On the complete opposite spectrum of the First Transformation—Three-Headed Vritra—and the Third Transformation—Recoiless Storm, Joyless Slaughter wasn't an offensive one at all.
It was not as simple as letting Echoes of Ad Infinitum infiltrate the targets' minds.
Such a blatant infiltration would not only be temporary but would also attract backlash, ruining all plans.
Kai only used these Echoes in the most drastic circumstances, like he had done so during the Zouken Matou's Inheritance incident.
At that time, he needed to keep the Heroic Spirits and all the Characters rooted to their spots as he created the House Common Room.
Those Echoes were nothing but a temporary burst of Confusion, cutting off all thoughts, preventing their bodies from acting out despite their minds' urgings. These Echoes lingered on the surface as they didn't fear getting found out, their nature being instantaneous and bombastic.
The Echoes of Joyless Slaughter went much deeper than that.
They remained in a complete state of hibernation, slowly parasitizing the targets' mindscapes. Not only did they actively mold themselves, acting like they belonged to those mindscapes, but they also subtly influenced the targets' thoughts and decisions.
It was all for that last moment when, getting the parent AI's nod, they could explode—injecting Kai's command in the mindscapes.
During the Third Stage of the Tournament of Worth, on Island X, something like that happened to two of the four Supreme Generals as well.
During the final battle, when Dumbledore and Goddess Xenomorph had attacked Mewtwo and Jon Snow, the Night Lord, they had truly believed that it was their decision.
Neither had they questioned the spontaneous thought that made them act against the other two Supreme Generals, but they had also not resisted it at all.
And why would they, when the command had originated from their minds?!!
Joyless Slaughter was such a powerful, broken transformation that, once unleashed, there was almost no chance of going against it.
And, as such, it also exacted a heavy toll on Kai's body.
Kai's mindscape, the Ad Infinitum, relied heavily on his physique to maintain itself. During the initial phase of creating the mindscape, if he hadn't had Selfless Breathing to reinforce his physique, then he would have never succeeded against the Supreme Generals. Instead, he would have died much before even attempting the Tea Ceremony for the last time.
That's why Kai liked to store Echoes in others' minds in semi-hibernation mode, collecting info that lingered on the surface.
The Joyless Echoes of the Second Transformation, though, needed to leave their total hibernating state together!
The higher the number of these Joyless Echoes, the higher the weight on Kai's stamina.
Moreover, the stronger the existences slaughtered, the crueler the load on the Ad Infinitum itself.
It became even more ridiculous when the slaughtered existences were not only Storyline Characters, but also Heroic Spirits of unimaginable strength and willpower.
What kind of command the Joyless Echoes would release, and for how long those commands were being subtly brewing in the targets' minds… Even the tiniest divergence… Even the slightest nick from the hand of fate… And even the most instantaneous change of heart…
Anything could result in Joyless Slaughter's failure.
That's why the Second Transformation was a double-edged sword.
On one hand, it claimed to be a path to a sure victory, once released. On the other hand, it would also end the user's life if it failed.
But for Kai, who thrived on chaos and these extremities of total victory and utter annihilation, there was no innate power that represented him the most, other than Joyless Slaughter.
So, even if Gorgon's appearance was a point of no return for Zelretch.
For Kai, the point of no return was him unleashing the Joyless Slaughter, the mere activation of which had turned him into the Conspirator of Fate!
…
Just above Earth's atmosphere, with the starry space in the background, Enkidu and Gilgamesh came to a halt.
They had already stopped fighting when they sensed the descent of the Avenger Class Servant.
It was clear that the Servants that originally belonged to the Holy Grail War would be annihilated if Enkidu didn't help them.
However, just as Enkidu was about to deal the final blow, and just as Gilgamesh was about to reply to the call of his friend, yellow crystals danced in their eyes.
They were the Heroic Spirits of the highest quality.
It was nigh impossible that they hadn't realized something.
So, the command that the Joyless Echoes had released was also in consideration of their true nature.
For Enkidu, it was the command for help.
For Gilgamesh, it was the command to… reconsider, making him use a Skill that he had never considered using before because of its sheer ridiculousness.
"On my authority as the Ruler of this Holy Grail War," Enkidu said, lifting his right hand. "I command all Heroic Spirits to unleash their full potential—for mankind… and for themselves!"
Booooooooom!
Green-hued Mana exploded around Enkidu as he unleashed the remaining set of Command Seals—enhancing all Servants' strength.
Opposite him, sensing the disaster brewing in the shape of Gorgon, and seeing the farewell written in Enkidu's eyes, Gilgamesh sighed. "… I… am not doing it for the pathetic fools," he said. "This world deserves to be eradicated. What does it matter if it happens through curses… or salvation?! Haha…"
"You…" Enkidu's eyes widened. "… You lied to me…"
Gilgamesh grinned. "Yeah…" he nodded. "I had no way to deal with Angra Mainyu… Just wanted to push you to put your best in the fight…"
Enkidu should have felt anger.
Yet, he found his expression softening.
"So… have you changed your mind, Gil?" Enkidu asked.
Gilgamesh scoffed. "No," he replied, looking up at the infinite, yellow stars. "Didn't I say I am not doing it for the pathetic fools…"
And suddenly, Enkidu knew what Gilgamesh was trying to say. "No! Don't do it!"
Noble Phantasm —
"… I… am doing it for you…" The King of Heroes said, all stars vanishing from his eyes, becoming one. "Sha Naqba Imuru…"
— The Omniscient Omnipotent Star!
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AN: The original scenic image of Enkidu and Gilgamesh is available in this chapter.
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