Spring, 700 SC
In the center of the Golden Lotus continent, there stood a shining city on a hill. This city, Tianzhou, was the capital of the Jade Mountain Kingdom, and some said it was the most important city in the world.
That day, in the 700th year of the Snake Calendar, Tianzhou was under attack by the Ox Demon King, a cultivator who some considered to be the most powerful yaoguai in all of Diyu.
A man with the head of an ox wearing the flamboyant Dao robes of a cultivator cut through dozens of warriors with his broadsword. Wind whistled through the nine rings attached to the broadsword as it soared through the air, cutting men in half and cleaving flesh from bone. Effortlessly, the Ox King cut a bloody crescent through Tianzhou as he moved toward the tallest building in the center of the city.
The Ox King had almost reached the top of the thousand-step staircase when his path was suddenly blocked. In the space of a blink of an eye, a man in pure white robes appeared at the top of the stairs.
This was the Dragon Immortal, one of only three immortals in all of Diyu, though the items he wore upon his body were so modest that it bordered on impropriety. He wore only plain white robes without design or decoration, and he carried only a simple sword with a thin blade.
"Dragon Immortal," the Ox King said, "I see that you have finally shown your cowardly face. "Face me now so that I may consume your flesh and ascend to immortality as I so rightfully deserve."
"My followers," the Dragon Immortal said, speaking first to the surviving cultivators in a profound insult to the Ox King, "I command you to flee the city now."
Without hesitation or argument, the surviving followers of the Dragon Immortal disappeared in a gust of wind.
"Will you run from my challenge, cowardly dragon?" the Ox King said as he pointed his broadsword at the Dragon Immortal. "I would rather not chase you to all four corners of the world."
"Foolish ox," the Dragon Immortal sighed. "Surely, even with your qi circuits degenerated by demonic cultivation, you have noticed the gaping wound that the Dao has recently suffered. If you use sacred techniques here, you risk heavenly tribulation of the highest order."
"That's why I come here today," the Ox King said, smirking. "I knew that you would be too cowardly to use your techniques with the Dao unsettled. Unlike you, I am willing to risk heaven's wrath for my ambition. Your time has passed, Dragon Immortal! Only the bold deserve to walk in the realm of immortality!"
The Dragon Immortal sighed before saying, "You fool. I do not need sacred techniques to defeat a mere yaoguai king. This immortal body and this single sacred treasure will be more than enough to kill you." The thin blade twirled in the Dragon Immortal's hand as he took up a fighting stance. "Step forward if you wish to earn the wrath of both me and the heavens."
The Ox King took a single breath through his bestial nostrils before empowering his body with a sacred technique. He exerted so much qi in that moment that every mortal in Tianzhou died in an instant.
In a flash of furious motion, the Ox King closed the distance between himself and the Dragon Immortal. The Nine-Ring Broadsword flew at the Dragon Immortal in a merciless attack, and each swing missed by a hair's breadth. With the minimum necessary movement, the Dragon Immortal dodged every attack before, after the fifth swing, responding with an attack of his own.
The Dragon Immortal's wrist twitched for an instant, and the Ox King was cut deeply in the chest. Surprised by the speed of the attack, the Ox King fled backwards as the Dragon Immortal lazily flicked the blood off his sword.
"The difference between us cannot be overcome with sacred techniques," the Dragon Immortal said as the Ox King fell to one knee. Such an injury would kill a normal person, but the Ox King was able to heal from the injury in just a few seconds. For those seconds, however, the Ox King was unable to fight.
Stepping forward with slow, languid movements, the Dragon Immortal said, "Return to the Burning Sky Kingdom where you belong, and accept your place below me."
The Ox King looked the Dragon Immortal directly in the eye and said, "I would rather die."
Speaking to himself, the Dragon Immortal said, "Those words are why this world will never know peace."
In an instant, the Ox King fled to the outskirts of Tianzhou. He surged with qi once more, and he transformed into a gargantuan quadrupedal ox the size of Diyu's largest mountain.
The ox roared with enough force to shatter every pane of glass in Tianzhou, and a bolt of lightning shot forth from the ox's horns with more force than a nuclear bomb. The bolt was aimed at the city, and the Dragon Immortal jumped in front of the bolt before it could strike the ground. In a single blur of motion, the Dragon Immortal took the bolt and redirected it far away from the city.
The bolt flew far off before finally detonating against a far-off mountain range. Upon making contact, the bolt detonated and carved a new canyon into the mountains that would serve as a major trading lane in the years to come.
Once more, a deafening roar assaulted the Dragon Immortal's ears as the Ox King reared back and prepared to charge at Tianzhou. If the momentum of that mountain-sized ox was not halted, most of the city would be destroyed. With each passing moment, it became clear that the Ox King's plan was to force the Dragon Immortal to fight in a certain way by threatening the city.
The Dragon Immortal moved forward to stop the Ox King's attack. Just as the Dragon Immortal reached the ramparts of Tianzhou, the Ox King used another sacred technique to empower his body.
Two great forces moved toward one another with the intention of colliding when their collision was interrupted. A massive pillar of light shone down from the sky and struck the Ox King.
The mountain-sized ox screamed and thrashed against the will of heaven as the light pillar pinned him to the ground.
"I warned you," the Dragon Immortal said simply as he turned his back on the ox. "The wrath of an immortal is nothing compared to the wrath of heaven. Goodbye, foolish ox."
The pillar of light bore down on the Ox King, and he was destroyed completely. Every cell of the once-mighty yaoguai was turned into sand, and his soul was destroyed. As a final act of defiance from the Ox King, the sea of sand that had once been his body fell upon Tianzhou and buried several of its districts.
On that day, an immortal fought with a yaoguai king, and five hundred thousand mortals died. As far as collateral damage was concerned, this number was low for such an event.