The gods of the God-Slayer world are less "gods" and more "personifications of phenomena," and as a result, their combat capabilities are immense.
According to a patch the original author posted on Twitter, the Authorities of Heretical Gods and God-Slayers are generally capable of affecting the entire globe.
Setting aside their individual destructive power for a moment, the sheer range of their Authorities alone makes Heretical Gods surface-level extinction threats.
Then there is their individual destructive power.
Take the war god Verethragna as an example. The destructive force of his White Stallion incarnation, when fully unleashed, is equivalent to that of a solar flare.
It can be said that the individual destructive power of a Heretical God is also terrifying.
Overall, after the retcon patch that sent their power levels skyrocketing, Heretical Gods are characters no weaker than the Lostbelt Kings of the Type-Moon world.
So, if Heretical Gods are so ridiculously powerful, how do God-Slayers even exist?
The answer is simple.
The machinations of the god of fate and…
Heretical Gods are all arrogant, reckless fools.
The first God-Slayer was able to slay a god because a certain war god got high on the thrill of watching a battle, and in a moment of pure impulse, picked up his own sword and lopped off his own head.
Then, a passing soldier picked up the sword that the war god had used to slit his own throat, walked over to another god who was also high on battle-lust, and stabbed him.
And thus, the world's first God-Slayer was born.
Yes, that god just died. Like that.
High attack, low defense, and no defensive measures whatsoever.
Even Sirin isn't that reckless.
Heretical Gods, every last one of them, are in the terminal stages of recklessness.
The Heretical Lugh had probably been taking things seriously.
After all, his enemy was a demigod who bore an aura similar to his beloved son.
And his beloved son was considered a top-tier great hero, even within the entirety of Celtic legend.
Aside from Fionn, who had a habit of offing his ancestors at the drop of a hat, his own son was undoubtedly the most outstanding of Celtic heroes.
Facing a young man with an aura so similar to his beloved son's, it was only natural that he would have to respond in kind.
But—
He was ignorant.
He had no idea what a hydrogen bomb was, nor did he understand nuclear fusion.
Coupled with the fact that the Key of Erosion had amplified his arrogance…
He chose to face-tank the hydrogen bomb.
"That was… quite a peculiar experience."
Lugh, who, for the first time since his birth, had felt the sensation of being consumed by heat and burned to ashes, remarked from the center of the devastated crater.
"For me, the God of the Sun, to be killed once by the power of light and heat."
The second-generation atomic bomb—the hydrogen bomb—is a thermonuclear weapon.
It is a three-phase bomb based on the principle of nuclear fusion.
The deuterium-tritium reaction is the first step of the fusion process, and it releases a temperature of around 800 million degrees Celsius.
Subsequently, the rate of nuclear fusion continues to rise along with the temperature. When the fusion reaction reaches its peak, the temperature at the center of the hydrogen bomb will soar to around 1 billion degrees Celsius before gradually decreasing.
The average temperature of the sun's core is fifteen million degrees Celsius.
Though both are forms of nuclear fusion, the reaction rate of a hydrogen bomb is far faster than that of the sun.
As the God of the Sun and Light, the Heretical Lugh possessed an Authority that allowed him to absorb light and heat.
But—
A temperature that casually exceeded that of the sun's core…
Was a bit beyond his absorption limit.
He had died once.
However—
Fortunately, as a sun god, he would not perish from a single defeat.
The sun sets, but it shall rise again the next day.
This is a law of the world.
"So, just how many health bars do you have left?"
Back in the ravaged area, the young man looked at the God of Light, who seemed completely unharmed, without much surprise.
To have taken down one health bar was already an excellent development.
For a sun god who embodies the concept of rebirth, resurrection was a basic move.
If the Heretical Lugh had been taken out by a one-shot from an H-bomb on their first encounter, he would have lost all face.
"Morning, noon, and evening, and then the curtain falls."
Even after being hit in the face with a hydrogen bomb, the Heretical Lugh showed no anger. Instead, he calmly revealed the fact that he could be resurrected three times.
"When the sun sets for the fourth time, I shall fall."
Then, He extended his strong, powerful hand.
And then—
The divine spear that slew the king of the Fomorians, Balor of the Evil Eye, Brionac, and the demonic sword passed down to Lugh by the sea god Manannán, Fragarach, materialized in his hand.
"A very interesting method of attack," He commented, gripping the two renowned treasures of Celtic mythology.
And then—
A magnificent divine aura surged from his body.
Like lava tearing through the earth's crust.
The fierce solar flames seemed to break through all restraints, threatening to vaporize everything in the vicinity.
"But—"
"The same trick won't work twice on a skilled warrior."
This was a fact.
Heretical Gods were not training dummies.
The Heretical Lugh had lost a life in an instant entirely because he had a brain cramp and chose to face-tank a hydrogen bomb.
If he had wanted to dodge, he never would have been hit.
"Come, let us begin our next round!!"
The god-king, experiencing the joy of battle for the first time in a long while, once again brandished his sword and spear at the young man who so closely resembled his beloved son.
But—
The young man opposite him did not raise his spear.
And then—
The Heretical Lugh discovered to his astonishment…
He couldn't move.
It was as if a thousand mountains were pressing down on him.
The earth itself was releasing its power, binding him.
The Heretical Lugh's expression turned grim in an instant.
He…
Had been outplayed.
"The battle is already over."
Confirming that the enemy needed to be killed three more times before he would fall for good, the young man smiled faintly and snapped his fingers.
The Herrscher of Reason could simulate more than just technology.
It could also simulate the Authorities of other Herrschers.
For example, the Herrscher of Rock, who commands gravity.
"A total of four times to kill you, is it?"
The young man, who had already applied a gravitational lock on the ground, smiled as he spoke the name of the spear in his hand.
"Well then, this is the second time."
Originally an anti-army Noble Phantasm meant for throwing, Gáe Bolg had been modified by Cú Chulainn himself for anti-personnel use, becoming his signature killing move and trump card.
It is a technique that reverses the "causality" that signifies the order of events. The moment it is unleashed, the "effect" of "the opponent's heart is pierced" is created first.
The "cause," "the spear strikes because the heart was pierced," occurs afterward.
I must stop it!
Bound and temporarily unable to break free, the Heretical Lugh roared.
"Brionac!"
That was the name of the treasure he held, a weapon whose power was absolutely superior to Gáe Bolg's!
But—
Brionac did not respond to its master's call.
Dark red patterns had long since spread across the two Celtic treasures.
The Authority of the Herrscher of Erosion could do more than just amplify emotions.
Unimpeded, the demonic spear known as Gáe Bolg pierced the chest of its former master's father.
Blood splattered.
The Sun God, his heart pierced through, felt the light gradually fade from his eyes.
And then—
A twilight-colored glow lit up his body.
He was about to revive.
"Fragarach, on standby."
Faced with this scene, the young man smiled faintly and called out the name of the second of the two great Celtic treasures.
"And now, shoot him down, Brionac."
PS: For some reason, I feel like Big Dog's dad died a rather tragic death.
PS2: Regarding the earlier discussion about the instantaneous power of an H-bomb being insufficient...You have to realize, the average temperature of the sun's core is only about fifteen million degrees.A being that can withstand one billion degrees... what kind of monster would that even be?