It was as if dry firewood had touched a fire, and when Lu Xuan transported his true qi, the condensed innate aura in the sky suddenly turned into Dao Dao clear qi, and poured into his eight veins of the Qi Sutra along Lu Xuan's Heavenly Spirit Acupoint. Lu Xuan was like drinking elixir at first, but soon he felt that his meridians were like soup boiling, and the abundant aura almost burst his body. Fortunately, when he was in the Xuanfu Forbidden Land, he was added by thousands of thunders, and both his physical body and meridians became several times stronger than before, so he could still persevere.

Half an hour later, Lu Xuan's eyes were red, and he felt that he had reached his limit.

He hurriedly stopped here, not daring to continue, and instead began to digest the huge innate aura in his body.

One week, two weeks, the true qi in Lu Xuan's body was running like a crazy wheel, but even if the speed of his cultivation was incredible, it was not so simple to completely refine the spiritual energy in his body.

Before you know it, five days have passed.

When Lu Xuan opened his eyes again, he felt refreshed, and even the cave where he couldn't see his fingers seemed to be much brighter. Looking at the depths of the dantian again, the true qi water mass that had originally swelled several times had turned into a small pond at this moment. And in the middle of the pond, a small cultivation seed was quietly erected on top of the true qi, and the top of the seed had already cracked, and a small, green seedling stood out, facing Lu Xuan's gaze, glowing with amazing vitality.

Lu Xuan could hardly believe his eyes.

In the middle of foundation building, it was completed in just two days!?

He repeatedly confirmed that he was sure that he had seen it correctly, and that he had indeed entered the realm of the middle stage of foundation building. This speed was beyond his imagination, according to Master Yue, he needed a lot of innate aura to cultivate, but it was much slower than ordinary people, but now it seems that this is not the case.

Although Lu Xuan was overjoyed, he also knew the truth that he couldn't swallow a fat man in one bite. He has just entered the middle stage of foundation building, and the first thing to do is to be stable, not to practice without moderation. He simply stood up and dispersed the Xuanfu Spirit Gathering Array, planning to take this opportunity to go to the underground fire vein to see what was going on.

Ling Bo flew across, and in the blink of an eye, he came to the bottom of the northern rock wall.

In the past few days, it was the first time that Lu Xuan had come to the place where the tongue of fire was spitting. Looking down, it was indeed a deep crack, the widest point in the center was large enough for one person to enter and exit. The crack had been scorched by the flames for many years, and had been scorched black as ink, covered in a thick layer of ash. He tried to peek into the cave, but all he could see was strange rocks and ashes fluttering, like a tunnel to the Yellow Springs Hell, with a mysterious and terrifying taste.

Lu Xuan settled down, withdrew a long distance, and waited for the tongue of fire to erupt.

A moment later, a flame rose into the sky, roaring for a moment before vanishing. When the flames dissipated, Lu Xuan took a deep breath, flew over, and jumped into the crack without hesitation.

As soon as he entered, Lu Xuan felt a strong heat wave hit, a few strands of hair were scorched in a blink of an eye, and his body felt as if he had been pricked by steel needles. He had already prepared, and immediately transported the Jade Pool True Technique, and after the extremely pure water vapor True Yuan spread all over his body, he immediately felt much better.

This crack is almost straight down, fortunately, there are protruding strange stones all around to borrow, Lu Xuan is jumping down while estimating the time, if he can't get out of this crack within half an hour, then he must escape from this place immediately, otherwise the tongue of fire will go and return, and he will only have one way to go.

Fortunately, this crack was not as long as Lu Xuan imagined, and in the blink of an eye, Lu Xuan felt that a red light flashed in front of him, and he had already stepped on the other side of the land under his feet.

This is another underground cavern, but the scale is not so large, there is a wide crack in the center of the cave, in which the flames are churning, the heat wave is rolling, and it is all rolling magma. Lu Xuan felt as if he had stepped into a steamer, the scorching breath was almost difficult to breathe, and even after opening his eyes for a long time, he felt that his eyeballs hurt.

This is indeed an underground fire vein, and what is displayed in front of Lu Xuan is just a drop in the ocean.

But even so, Lu Xuan still felt that it was unbearable, so he ran the Jade Pool True Technique with all his might, tried his best to resist the surging heat wave, and then picked a flat place to sit cross-legged.

Although he really wanted to cultivate the Yi Bone Sutra here, with his current cultivation, it was really difficult to practice here. What's more, flames erupt every other hour, and if you don't leave in time, you're sure to die. So even if Lu Xuandang made up his mind, it was better to collect the aura of the fire vein as much as possible here, and then return to the Xuanfu Spirit Gathering Array to cultivate the Yi Bone Sutra.

When Lu Xuan tried to introduce the fire vein aura into his body, he immediately knew what it meant to burn inside.

Although this fire vein aura is mixed, it is far less pure than the innate aura formed by the Xuanfu Gathering Spirit Array, but after all, it is a fire type aura, and it is fierce and domineering. Lu Xuan felt as if he had fallen into that piece of magma, not only his body was skinned, but even his internal organs were about to be burned to ashes.

And just when Lu Xuan couldn't bear it, the pure true yuan in the lower dantian suddenly started to work on its own, protecting the meridians all over his body, and making him feel a lot more comfortable.

Thanks to the true trick of Yuchi, he didn't fall short.

But even so, Lu Xuan still didn't last long. But after a quarter of an hour, he could no longer hold on, and he felt that the blood on his body was almost boiling, and his mind began to become trance. At this time, he also noticed that the magma in the crack began to become agitated, and it was obvious that the next eruption was not far away.

He got up on the spot and followed the path he had come from back to the underground river above.

Opening the Xuanfu Gathering Spirit Array again, Lu Xuan finally began to prepare to cultivate the Yi Bone Sutra.

Lu Xuan now has two top-level exercises in mind, one is the Jade Pool True Recipe, and the other is the Yi Bone Sutra, but compared with the two, although the Yi Bone Sutra is not an exercise for cultivating the true element and enhancing cultivation, Lu Xuan still ranks the Yi Bone Sutra in front of the Jade Pool True Technique. Because this Yi Gu Sutra is not only a secret that Buddhism does not pass on, but also the only way to shape the foundation.

The nine-story platform starts from the earth.

This immortal bone is the foundation of the monk, although the strength of the cultivation cannot be judged according to the weight of the immortal bone, but two monks practice under the same conditions, the one with the heavy immortal bone must be far easier to cultivate than the one with the light immortal bone.

If the monk is compared to a tree, then the immortal bone is the trunk of the tree, and the meridians, qi and blood are the branches and leaves, and the fruits.

And the ultimate goal of cultivation is to be reborn, to exchange the holy womb for the mortal fetus, and the immortal bone for the mortal bone. Therefore, if one day Lu Xuanzhen can turn the mortal bones of his whole body into immortal bones, it will be tantamount to the body of a half-immortal, although he may not be able to really live forever, but it is enough to communicate with heaven and earth, and the Tao is mysterious.

With Lu Xuan's current knowledge, he can only realize the importance of immortal bones, but he is still confused about what benefits exercising immortal bones can bring him.

However, he believed in Master Yue, and also believed that cultivating the Yi Bone Sutra would be the most important first step on his cultivation path.

So Lu Xuan settled down and practiced.

The cultivation method of the Yi Bone Sutra is completely different from ordinary exercises, it uses the physical body as the furnace, and the innate aura as the medicine, and the fire aura is refined into thousands of wisps of breath that go straight to the bones of the body. The fire-based aura that Lu Xuan had collected in the underground fire veins just now was now gathered in the lower dantian, which was clearly distinguishable from his own true yuan, and water and fire were incompatible. According to the method of the Yi Bone Sutra, Lu Xuan began to absorb a large amount of innate aura, and saw that the large amount of aura in the Xuanfu Spirit Gathering Array rushed straight towards Lu Xuan, and submerged it in the blink of an eye.

At this time, Lu Xuan was like gluttony, and he devoured the aura in the magic circle by dividing it by two.

The fire in the dantian soared into the sky, and the innate aura was repeatedly burned and tempered in every way. Then it turned into wisps of spiritual light, through Lu Xuan's flesh and blood, attached to the bones. At that moment, Lu Xuan felt as if countless ants were gnawing at his bones, and then, suddenly, there was a sharp pain from the depths of his soul, like a stormy wave.

Lu Xuan snorted and almost fell to the ground.

The sharp pain was stronger than wave, and even Lu Xuan's tenacious temperament almost kept moaning. In the dark, it was as if someone was wielding a huge hammer, smashing the bones in Lu Xuan's body, and then reshaping and smashing them again, and so on, it was like dead and alive.

I don't know how long it took, when the flames in the dantian burned out, Lu Xuan collapsed to the ground like a prostration.

Lu Xuan lay on the rocks on all fours, letting the waves wash over his body, he felt that he had no strength in his body, and even his soul was a little uncertain. During that period of time just now, he longed for all the tricks in his body to be fully opened, so that the terrifying heat wave could be released, but he was born with only one trick, but it was like a tightly knit furnace, and he didn't waste the slightest innate aura.

However, as Master Liyue said, his stubborn qualifications are unique for cultivating the Yi Bone Sutra.

Although I have endured all the hardships, I will definitely benefit a lot in the future.

Lu Xuan rested for a moment, struggled and took out a jade pendant from his arms. This jade pendant was the thing he used when he was a guide to weigh the immortal bones of the cultivation seeds, and now it is just right to see if his immortal bones have grown. He put the jade pendant in the center of his forehead, and his luck was concentrated, and he took it in front of him later, but saw a few words flashing on the jade pendant.

Eight taels of fairy bones.

Compared with more than a decade ago, there is no change at all.

Lu Xuan was a little frustrated, but after thinking about it, he was only cultivating the Yi Bone Sutra for the first time, how could he have achieved something? The immortal bone was too worthless. So he mustered up his spirits and prepared for a long battle.