The Formation Orb divided into its yin and yang components and slowly merged with the realms of yin and yang before Lu Yun.
“It looks like the two tombs were based on the Formation Orb to begin with. Now that the real deal is here, it can naturally draw upon the power of the two sides to reassemble them.” He cracked a smile.
There were also myths about yin and yang tombs on Earth, but the planet was in the Degenerate Age and had almost no heavenly qi at all. 
The environment made it impossible for yin and yang tombs to take shape on the planet.
There were records of such tombs in his sect, but Lu Yun had still needed to identify the key relationship between the two tombs using both the Tome of Life and Death and the Formation Orb.
This spot was where the yin and yang tombs originated from, and the key to breaking the layout and combining the two was the Formation Orb. The Formation Orb had been divided into two lesser connate-grade treasures before; Lu Yun had a pet theory that whoever set up this place was responsible for that, as well.
The two orbs gradually melded into the origin of the two realms, guiding them to become one again. An indiscernible tremor passed through the air as the process began, unleashing spatial power.
The two orbs vibrated, forming a bizarre layout along with the yin and yang tombs. The moment the layout was completed would be the moment the two tombs became one again.
“Waugh!” a piercing scream broke the silence as a scarlet figure lunged at Lu Yun.
“A scarlet yin spirit!” Lu Yun tensed; he hadn’t expected to see this color of yin spirit here!
On its own, the spirit wasn’t particularly powerful and wouldn’t pose that much of a threat to immortals. In great numbers, however, they were terrifyingly deadly. Back in Azure Province, scarlet spirits had killed, and devoured, many dao immortals, leaving only fleshless skeletons behind.
They were very hardy, and could bypass an immortal’s defenses. If one allowed them to draw near, death was the only possible end—not even arcane dao immortals were exceptions. If there was one such spirit here, that meant there could be many more floating around.
Bedazzling violet light flashed through the air and scattered the scarlet spirit. Lu Yun grasped Violetgrave firmly, exercising the highest level of caution.
“Wah! Wah! Wah!”
A chorus of strange cries and shrieks rang out as hordes of scarlet spirits swarmed him in a collective tsunami, shaking the two Formation Orbs as well.
“Dammit!” Lu Yun sprang into action. One singular spirit was no cause for worry, but so many of them launching suicide charges would be enough to undermine the merging Formation Orbs from the collateral damage alone.
With a flip of his hand, he summoned the Sugato Sword and bade it disassemble into a deadly stream of swords that shot straight into the scarlet spirits.
An explosion of sound rocked him backward, sending blood streaking down from the corner of his mouth.
Too powerful! Lu Yun’s heart sank.
Each of the spirits would individually rival only a golden immortal. When come together as an aggregate, however, theirs was a shocking force that couldn’t be stopped.
In Azure Province, he’d shielded himself with hellfire and prevented the yin spirits from getting close, or even detecting him at all. Now, however, he wasn’t trying to protect himself, but had to stop the spirits from destroying the layout being formed by the two Formation Orbs.
With a single thought, Lu Yun tapped into the small world that all void realm cultivators constructed inside themselves and unleashed endless waves of heavenly power.
“Die!” With a backhand push, he sent a shockwave through the dense swarm of yin spirits, carving out a palm-shaped void of six hundred meters in its wake.
He’d killed thousands of spirits with a single attack; the heavenly power of void realm cultivators was their bane. Flipping his wrist again, he called upon hellfire and deployed a black hellfire dragon that rampaged through the air. Yet more countless spirits disintegrated under the attack.
“Wait, this won’t do! Hellfire is too strong, and the special power it contains will change the layouts here.” Lu Yun studied the environment and observed the minute changes that the hellfire had left behind where it touched. With prolonged exposure, the layout of the world’s lungs would be destroyed completely.
Hellfire was just too unique.
Many powerful beings had tried, and failed, to destroy this locale. In the end, they’d had no choice but to bury it. Hellfire, however, could singlehandedly tear the layout apart. Violetgrave was right—it was indeed the greatest flame in the world.
“Dao immortals can’t survive here... I’m pretty sure any of them would be killed by the intangible lungs as soon as they set foot in here!” Lu Yun retracted his hellfire and gathered heavenly power instead.
Fueled by great heavenly power, combat arts of the Primeval Era sprayed out in all directions, slaughtering the yin spirits.
“This isn’t a solution… I can replenish my heavenly power, but not at this rate! If this goes on, I’ll run out of energy before the Formation Orbs finish merging!” Lu Yun could return to hell at any time and restore his inner energy, stamina, and willpower. However, he couldn’t restore his reserve of heavenly power.
“It’s a shame that Beigong Yu’s dead. The Scaled-Dragon King is also in the yin tomb, so I can’t summon him here...” He was growing agitated.
There were too many yin spirits here; it seemed as if they were pouring forth from an inexhaustible spring. It was next to impossible for Lu Yun to guard the Formation Orbs on his own.
Bing Ling and Bing Xuan were arcane dao immortals and thus couldn’t be mobilized from hell. Beigong Yu was currently a statue outside the kunpeng nest. The Scaled-Dragon King had been thrown into the yin tomb. Lu Yun couldn’t summon either of the two until the yin and yang tombs finished merging.
He was on his own.
“My sword!” Inspiration struck Lu Yun. He recalled when Violetgrave had killed the divine spirit residing in the giant lungs with a single slash. It hadn’t been an attack of sword technique, but of sword dao. “If she can do it, I can do it too.”
With a wave of his hand, the sword energy of the Sugato Sword formed a protective circle around the Yin and Yang Formation Orbs while Lu Yun rushed the scarlet spirits with Violetgrave. He mentally simulated Violetgrave’s stroke, then thrust the sword forward into a stabbing motion.
1. The Three Ages of Buddhism are three divisions of time following Buddha's passing:
Former Day of the Dharma: also known as the Age of the Right Dharma (正法), the first 1,000 years in which Buddha's disciples are able to uphold Buddha's teachings. Cultivators are highly confident, acts of kindness abound, and many reach the dao.
Middle Day of the Dharma: also known as the Age of Semblance Dharma (像法), the second 1,000 years, which only resembles the right Dharma. Focus turns to scripture and images of Buddha, but still bears a great deal of resemblance to the first age.