"This is also a kind of secret technique. There are no movement techniques in spirit techniques," Cui Yu said with a slight smile.

"Boss, a demon beast is coming, at the fourth-tier level," Little dragon's voice spread in Li Lin's mind.

"Roar..."

From a distance, a huge roar came, and the violent sound waves shook the space like muffled thunder, making Li Lin's ears somewhat numb.

When the roar fell, a huge demon beast appeared in front of the two. This demon beast was massive, with a body size of three hundred meters, covered with sharp spines half a meter in size, spreading out like fish fins.

This demon beast was golden all over, with a head somewhat similar to that of a blood lizard. In its gaping mouth, a thick breath spread out, covering the sky with a yellow glow. Its four sturdy claws were also covered with a thick layer of spines, and its tail had a sharp, tens of meters long spike.

Under this massive demon beast, a tremendous oppressive force spread out, forcing Li Lin and Cui Yu to mobilize their true qi and spirit power to resist.

"A Earth-type demon beast, a fourth-tier mid-stage Ironback Lizard," Li Lin said softly, then a slight smile appeared on his lips. Finally, he encountered a fourth-tier demon beast. He was in need of demon cores. With a demon core, his strength could continuously improve. If he kept taking elixirs, not only would the effects not be as good as those of demon cores, but it would also be too costly. At his current level, Li Lin estimated that even spending tens of millions of gold coins on elixirs would only allow him to barely break through one level. If he reached the level of a martial general, it would be terrifying. He estimated that hundreds of millions of gold coins would not be enough to break through a single level of cultivation.

Therefore, to break through in cultivation, he should mainly look to devour martial and spirit practitioners, or to devour demon and spirit cores.

"Three years have passed, huh? Humans have come again." Watching Li Lin and Cui Yu, the Ironback Lizard spoke human language, spewing out a huge gust of air. Its strength was not low at the mid-stage of the fourth tier.

"Do you really think you can stop us? Get out of the way," Cui Yu said sternly to the Ironback Lizard.

"Hmph, such a big tone from a little kid. I'll just use you to pick my teeth," the Ironback Lizard roared, its aura beginning to surge violently.

"Only mid-stage of the fourth tier? Then, your demon core is just right for me to take," Li Lin's expression darkened. A mid-stage fourth-tier demon core could probably allow him to break through from the fourth level of the Martial Soul to the fifth level. Naturally, he had to claim this demon core.

With a change of hand seals, a violent airstream suddenly spun up in Li Lin's hand, turning into a small tornado vortex that abruptly appeared in the sky. The tornado vortex grew rapidly against the wind, instantly becoming a giant tornado vortex of hundreds of meters.

The howling tornado vortex swept up the giant rocks from the ground, which were then crushed into powder by the fierce wind force.

"Hmph, I'll use you to pick my teeth first!" Watching Li Lin, the Ironback Lizard's anger was because it only felt Li Lin's fourth level Martial Soul cultivation strength. With a fourth level Martial Soul, it naturally did not fear him. From its huge mouth, a deep roar echoed through the space.

Immediately, a surging earth attribute energy flow burst out from its mouth.

"Human, die!" The Ironback Lizard's huge mouth issued a roaring sound, and the surging airflow turned into an attack that struck towards Li Lin.

"Despicable beast, seeking death." Li Lin snorted coldly, changing his hand seals again. A massive true qi surged into the tornado vortex, and he shouted deeply, "Wind Rolls the Remnants."

As Li Lin's true qi was injected, the tornado vortex instantly swelled, lifting a layer of soil from the ground. Numerous cracks appeared, and the soil layer swept into the sky, overwhelming everything in its path.

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The two massive forces collided in the air like lightning. At the moment of collision, the space almost became silent, followed by a huge explosion...

"Boom boom!"

The two forces collided fiercely, releasing terrifying energy. In the sky, energy filled the air violently, and under the terrifying energy, the space began to ripple slightly.

At this moment, Li Lin made another move, his true qi forming wings on his back. Using the Wind Wings, combined with Floating Shadow, his body almost turned into a flash of lightning, instantly appearing behind the Ironback Lizard.

"Now, die." A faint voice came from Li Lin's mouth: "Fiery Explosion."

With a movement of his hand seals, a palm-sized fireball in his hand spun violently, cutting through the space. The entire space's temperature suddenly soared, and the powerful aura pressed down, directly enveloping the surrounding space.

The fireball quickly expanded, tearing open a fiery arc in the space. A terrifyingly hot oppressive force spread out like a tsunami.

Feeling this terrifying force, the Ironback Lizard finally began to fear and retreated, but it was already too late. The terrifying flames dispersed, immediately enveloping it.

"Boom boom..."

The fireball exploded in mid-air, shaking the space with violent ripples. The unparalleled hot flames swept across the sky, and visibly, the Ironback Lizard was engulfed by the firewave. Its massive body was overwhelmed by a violent and hot force.

A mid-stage fourth-tier demon beast, usually difficult for a sixth level Martial Soul to deal with, but that doesn't mean all sixth level Martial Souls are incapable. Although Li Lin was only at the fourth level of Martial Soul, his actual strength had long exceeded his cultivation level. Killing this Ironback Lizard was not a problem at all.

"Sigh..."

When all the fiery energy dissipated into nothingness, on the ground in front of them, the Ironback Lizard's massive body lay charred on the ground.

Li Lin, without any politeness, retracted his true qi wings and instantly landed in front of the massive body of the Ironback Lizard. A long sword had already appeared in his hand, slashing towards the Ironback Lizard's abdomen.

"Crack."

With a cracking sound, sparks flew. This sword strike, despite the Ironback Lizard's thick spines, only left a shallow mark on its skin.

"Such thick skin," Li Lin muttered.

"Lin'er, use this to collect the demon core," Cui Yu said, handing over a black long sword. The sword blade was all black, emitting a smooth black luster, then she handed it to Li Lin.

"This is no ordinary item." Holding the black sword, Li Lin immediately felt that it was not a common spirit craftsman's work. The material was extraordinary. From its luster, it was probably at least crafted by a spirit general, and likely close to the level of a spirit commander. With this material, the black sword was worth at least a million gold coins.

At this point, Li Lin had already determined that Cui Yu was not as simple as a common maid, but he could not guess her identity. Along the way, Li Lin had tried to probe, but Cui Yu's answers were watertight, leaving Li Lin helpless.

"Shoo shoo..."

With one slash, the hard-as-iron body of the Ironback Lizard was instantly split open from the abdomen, and a mid-stage fourth-tier demon core slid out. The violent energy trembled, and Li Lin quickly collected it into a brocade box.

"Crack crack..."

"What a pity." Watching the thick hide of the Ironback Lizard, Li Lin felt somewhat pained. If he could have skinned it, its value would have been at least tens of thousands of gold coins. But now, they needed to hurry on their way and didn't have time to skin the Ironback Lizard.

"Here, this sword is not a common item," Li Lin handed the black sword back to Cui Yu.

"If you like it, just keep it. Consider it a gift from me," Cui Yu said with a smile.

"How could I accept this?" While Li Lin said this modestly, he quickly stored the black sword in his space bag, as if afraid that Cui Yu might change her mind. Such a treasure, worth over a million gold coins, perhaps even more, was not to be missed.

"Let's go. Hong Ling and the others may have already gone far. We need to speed up," Cui Yu said, looking around.

In a space without the sun, moon, stars, day, or night, the whole space felt oppressive, especially with the constant danger, making it even more so.

"Boom boom..."

From the distant sky, a series of sonic booms echoed within the space. In a forest, two blurry figures could be seen launching attacks.

"Boom boom!"

Massive energy fluctuations, the giant rocks on the ground were directly shattered, and towering trees were uprooted, swept away by the fierce power.

When the last bit of violent energy dissipated, Li Lin and Cui Yu's figures appeared in the space, looking at the body of a late-stage fourth-tier demon beast on the ground. Li Lin said, "The fifth late-stage fourth-tier demon beast."

"It must have been over a month now, right? Now we have killed fifteen early-stage fourth-tier demon beasts and ten mid-stage ones," Cui Yu said with a slight smile.

"Cui Yu, this demon core is yours," Li Lin said. For the first time in this period, Li Lin, the miser, felt embarrassed. All the demon cores from the beasts they had killed were collected by Li Lin. Now, he had over twenty demon cores.

"You keep it. The demon core isn't of much use to me," Cui Yu said with a slight smile.

"Alright then." Li Lin didn't insist and collected the demon core. During this time, without day and night, they could only estimate the time by counting the hours. They guessed it had been over a month.