Yang Qi had acquired a demon core from a Personal-Domain corpse king, which, if it were to be inlaid into a spell formation, could actually replicate the corpse king’s Heaven-Devil Domain. And anyone who wasn’t in the Personal-Domain Transformation who got caught in a domain like that would be killed.
Unfortunately, Yang Qi could not do that, nor could he consume the core directly. It was just too powerful. Perhaps if he broke through to the Space-Void Transformation, then he could use it.
In any case, the fact that he could kill a Personal-Domain Legendary was quite gratifying. Part of it had to do with the fact that his energy art was specifically designed to deal with fiend-devils.
If he had been fighting a human cultivator in the same level, it would have been a different story. At best, he might have been able to fight to a draw.
Given his current cultivation base, squaring off with people like Master Wind Gentleman or Unparalleled Lightning just wouldn’t work. People like that cultivated righteous and orthodox energy arts, and thus, would not be adversely affected by the Strength of the Hell-Crushing Godmammoth. Once Yang Qi reached the third Legendary transformation, though, things would be a different story. At that point, he could use the Grand Emperor's Pagoda to crush countless powerful heroes.
‘A demon core like this is a rare thing. I guess I’ll save it in my Hellfire Crucible for the time being, and refine it later.’
At the moment, the Hellfire Crucible rested in his Hell Portal, constantly burning the flesh and blood of the monsters he killed. Its flames were incredibly powerful, and could handle all sorts of magical treasures, even spirit stones. They surpassed the types of fire that ordinary people cultivated, such as Five Phases True Flame, Burning Sun True Flame, and even Heavenly Body True Flame. Yang Qi had the radiant fire of the legion of gods, the Cleansing Flame of the Heavenly World.
He also had the Grand Emperor's Pagoda in the Hell Portal, where it rotated above the Hellfire Crucible. Inside the pagoda, the remains of the asura were now a sphere of wriggling blood. That was the most precious thing to Yang Qi. Sovereign-grade spirit stones, spirit weapons or magical treasures didn’t even come close to the flesh and blood of a Never-Dying asura. Not even the five phases treasures.
He had been working with that flesh and blood for a very long time, and yet had still not extracted the full potential of its power. After all, there was a devil core in those remains, which contained never-dying magical laws. Obviously, Yang Qi’s cultivation base would need to be higher before he could refine that core, or use it in a spell formation.
As soon as the corpse king’s body entered the Hellfire Crucible, the Cleansing Flame of the Heavenly World began to transform. The faces of god-spirits appeared in it, almost as if each tongue of flame were one. As the magical laws of the corpse king began to burn, all sorts of strange phenomena occurred.
Because Yang Qi’s cultivation base was too low to absorb the magical laws, the best thing he could do was to burn them and use them to improve the Cleansing Flame of the Heavenly World.
As the pure flames burned his own true energy, his Strength of the Hell-Crushing Godmammoth continued to climb to new heights.
‘The legion of gods provides the spore-devil in the Hell Portal. Oh, master of countless devils, devil among devils, controller of hell, come forth!’
Yang Qi threw his hands wide, and a monster appeared within the Hellfire Crucible. Without hesitation, it absorbed the god-spirit flames, and even fused with the asura's flesh and blood, like a parasite would. Although the asura’s flesh and blood was something that seemed eternally indestructible, the Cleansing Flame of the Heavenly World had changed it.
Flesh and blood quintessence swirled around the new monster, until it was wrapped up like a chrysalis.
This monster was none other than the Hell Portal’s spore-devil.
Yang Qi was pushing himself to the limits, using all of the power of five thousand ancient megamammoths. He couldn’t surpass the limits of his own level, but this spore-devil could.
The spore-devil’s facial features resembled Yang Qi’s, except devilish in nature. His psychic elements were ensconced in the thing, making it very much like the out-of-body incarnations that certain cultivators created. It was like a second nascent divinity, and yet, was much more profound and enigmatic than ordinary second nascent divinities.
The spore-devil was the overseer of the Hell Portal, and using it to summon monsters vastly increased the possible pool of targets. Now, summoning monsters that were higher than Yang Qi’s level would be no problem. Although it was not an uncommon thing for energy artists to have out-of-body incarnations or second divinities that surpassed their own level, such entities ended up being autonomous to a certain degree. In contrast, the spore-devil was connected to Yang Qi on a deep level. If he died, it would vanish. In fact, with a mere thought on his part, he could destroy it.
“With a thought, the devil appears,” Yang Qi murmured in Godtongue, “and the pāramitā lily blooms….” 
The spore-devil began to twitch and wriggle, transforming as the cleansing flames washed over it. Numerous magical laws stirred inside it as the unique changes affected its life force on the deepest level.
Thanks to the powerful Cleansing Flame of the Heavenly World, the magical laws and corpse energy of the ten-thousand-year-old corpse king were already burned away.
Before, the flame had not been strong enough to burn away the asura’s flesh and blood, but with the additional fuel of a monster in the sixth Legendary transformation, they could burn hotter than ever.
Before, he had been able to burn and absorb the will of battle and slaughter that existed in the asura, but now, he was taking the quintessence of its flesh and blood. In fact, he could now finally see the asura’s devil core deep in that mass of flesh and blood.
“DIE!” Yang Qi shouted, slaughtering his way deeper into the hell monsoon, and the ancient sealing mark on the planar greyspace.
As for the fiend-devils which sensed his onslaught, they rushed to attack him. “Inverse Devil-Spirit Attack!”
A fiend-devil count reached out, summoned a huge bow and arrow made of true energy. The bow was thousands of meters from tip to tip, and the enormous arrow swirled with a massive vortex of devil energy.
The arrow was drawn to the limit and then released, piercing through everything in its path as it shot toward Yang Qi. However, it was no challenge at all to the Infernal Deity Spear, which shattered it into fragments. Then, the spear transformed into something like a bolt of lightning that smashed into the fiend-devil count’s chest, reducing it to a bloody paste. Before anything else could happen, the Hell Portal opened, sucking in the thing's remains, including its demon core.
This fiend-devil was many transformations below the corpse king from earlier, and thus, was quickly eaten away by the Cleansing Flame of the Heavenly World.
Yang Qi wasn’t even paying attention to that aspect, and merely advanced to the next challenge.
This was a fight in which he must continue onward no matter what deadly obstacles faced him. In this session of training and fighting, he knew that he could achieve progress that would be considered impossible outside.
After all, who but he could use a Legendary fiend-devil as mere fuel for fire to improve his true energy? In the Rich-Lush Continent, even Great Sages like the chancellors of the four institutes couldn’t even comprehend such a thing.
When the Young Lady saw the fight with the bow-wielding fiend-devil, she couldn’t help but murmur, ‘Heaven-Devil God-Exterminating Greatbow?’
That bow might not have posed a threat to Yang Qi, but that was mostly because of the low level of the fiend-devil he had fought. Had it been wielded by a more powerful enemy, things would have been different.
According to certain stories, there was a leader of the fiend-devils who resided in the depths of hell, a being who possessed wisdom regarding all aspects of hell. He was the fabled creator of the Heaven-Devil God-Exterminating Greatbow energy art, which had been designed to attack and kill members of the legion of gods.
There was no way that the true and full manifestation of the technique would be in the hands of some low-level fiend-devil. Clearly, what had been used was a subsidiary version. Even still, it was nothing to scoff at.
By the time the Young Lady recognized what she was seeing, Yang Qi had killed the thing and was continuing to advance through the hell monsoon. At that point, mournful bugle sounds rang out, as some greater fiend-devils summoned an army to besiege Yang Qi.
Instantly, black streams of smoke began to gather.
Each and every soldier in the army was a fiend-devil viscount, and there were over ten thousand of them, Lifeseizers all, a massive force arranged in tightly disciplined ranks. There were dozens of officers among them, Legendary counts, some of them in the fourth or fifth transformation.
Shockingly, all of the fiend-devils had enormous bows and devilish arrows. In the blink of an eye…. a rain of arrows was bearing down on Yang Qi.
In fact, the arrows actually made a spell formation of seemingly invincible power, which locked down space-time and made it impossible for the target to flee.
Yang Qi knew that this was nothing to take lightly. Without any hesitation, he entered the Grand Emperor's Pagoda and activated its defenses. As it hovered there, the arrows began to slam into it.
One by one, the arrows shattered, and Yang Qi absorbed their energy to improve his own.
By the time the rain of arrows ended, his aura was the type that could shake the heavens and topple the earth.
1. Pāramitā literally means “the other side of a bank or river; the opposite shore” and is an important concept in Buddhism. It basically means “perfection” or “completeness”, and refers to a realm that surpasses life and death. It can also mean “afterlife” or “salvation”. For more info, you can check out the Wikipedia article. In I Shall Seal the Heavens and A Will Eternal, there are “pāramitā lilies” or “resurrection lilies” which play an important part in both stories, but Er Gen is by no means the first author to have used pāramitā in his fiction.