In Tian Xu's mind, the body of the Immortal of the Holy Realm is composed of aura, so the various energy fluctuations in their bodies are also fluctuations transmitted to each other within the aura, and what is embodied on the outside is the energy exchange between the various parts of the aura that constitutes their body, that is, the increase of some of the aura energy, and the decrease of the aura energy of the other part, more detailed, these energies may also be different internally. But in any case, it is the energy exchange inside this group of aura, and there is no change on the outside.

The Immortal of the Holy Realm could cover the aura that made up their body with a layer of "skin" that had no energy fluctuations, completely covering up the energy exchange inside, making his detection useless.

This kind of cover-up may not be a simple passive cover-up, but a neutralization method to neutralize the energy fluctuations exchanged by the aura, which are almost completely imperceptible to the outside world and cannot be caught at all.

However, Tian Xu still found an opportunity to discover the other party.

The stealthy Immortal of the Holy Realm, while being invisible, will also detect the external situation, and as long as this external observation and detection action exists, it will inevitably have an impact on the signals of the outside world.

For example, if the other party detects the sound of the world through hearing, then he needs to absorb the vibration energy in the sound, when he observes the external image through vision, he will absorb part or even all of the light that transmits visual signals from the outside world, and when he feels the smell of the outside world through his sense of smell, he needs to absorb the molecules that carry the smell information from the outside world. In other words, although the immortals of the Holy Realm are only passive detection and do not send active detection signals to the outside world, they will also have an impact on the outside world.

As long as Tian Xu can detect this change in the signal of the five senses in the outside world, he will be able to detect the hidden information of the other party.

In order to achieve such a detection goal, he needs to make some improvements to his olfactory imaging.

The olfactory imaging he used to use was spent all his time trying to find more representative characteristic signals, identify and use them, and the vast majority of signals representing general characteristics were only treated as background and did not pay attention to them. If his olfactory imaging were to be compared to a photograph, almost all of his energy would be focused on the people in the photograph. The part of the environment that is used as a background is only used to make a reference with the characters when needed.

What he needs to do now is to find traces of P in the background photo of the person who has been P's drop.

This thing made Tian Xu quite unaccustomed to it. He tried to scan his surroundings and found that if he still used the original olfactory imaging method, he would need to inspect the suspicious points on the vast background inch by inch, and then carefully confirm them. Even if you don't actively send a signal to detect, it is quite difficult to achieve, and the main problem is that the speed is too slow. Now his olfactory imaging detection range can probably reach a radius of a little more than ten kilometers, such a large range, if you detect it once, it will take at least a few minutes to ten minutes, and when fighting, such a long time is enough for you to be killed by the other party hundreds of times.

If the detection range is narrowed, even if it is reduced to a radius of two or three hundred meters, it will take more than ten or dozens of seconds to complete the detection. During this period, if the opponent's position is moved, it is very likely that the detection will be useless.

The speed of detection must be accelerated, at least as it was in the original olfactory imaging. In other words, it is necessary to look at a real environment as if it were a real environment, so that the observed area can be seen at once.

This matter stumped Tian Xu all of a sudden. Even if the detection speed is slowly increased through training, it is estimated that it will not be increased too much, and it can be increased by one or two times, or even several times, but it still cannot meet his requirements, which is an order of magnitude difference.

Imagining the appearance of the improved olfactory imaging, Tian Xu involuntarily spread the olfactory imaging around and observed the surrounding environment. As the olfactory image swept over the formation that was hatching the giant egg, he suddenly noticed a problem: relative to the surrounding environment, the aura and energy near the formation were changing! Yes, it was changing.

In fact, it was that formation that was absorbing the heat and aura of the outside world. The speed of this absorption is not fast, and he usually does not notice. But at this time, his attention was focused on the surrounding environment, and the fact that the aura and heat around this formation were slowly disappearing, compared to the environment that had not changed significantly, it was as striking as a bright light in the night.

He tried to observe the anomaly again, but it was no longer so clear, and after thinking for a while, he finally figured out the crux of the matter, which was to observe from a different perspective.

The olfactory imaging perspective he usually uses to scan the surrounding environment is like the perspective of ordinary people looking at things, but the perspective that he just discovered that the incubation formation was abnormal was inadvertently switched to the inverted color mode, similar to the appearance of a photographic negative.

He flipped his perspective again, and the incubation formation became clear again, and the energy and aura changes around the formation became clear and abnormal again.

He understands that the key to this is the change in contrast brought about by the change of observation angle. It's like a legendary detective who put the black stubble in a razor on black paper and looked at it, giving out a handful of white stubble mixed in with it, and the trick is to find anomalies that are not obvious by changing the background.

He observed the surrounding environment again and again, and for this purpose, he refined more than a dozen different hidden formations, and gave these formations a certain function of absorbing information from the outside world, and after repeated practice, he found that this method should be enough to observe the hidden formations or the Immortal of the Holy Realm just like the original olfactory imaging.

After practicing, he discovered a new trick, that is, to quickly switch between normal observation and inverted color observation, when he just switched, the original observed image still has a certain amount of residue in his sea of consciousness, through the comparison of the residual scene and the scene that has just been switched in, he can more easily find the enemy's traces.

found a solution to the problem, Tian Xu was also in a cheerful mood, and the goal and task of entering the Medicine King Dou this time was finally completed.

Solving the problem of detecting the invisible Immortal of the Holy Realm made Tian Xu breathe a deep sigh of relief. It took him nearly ten days to complete this perception and the perfection of olfactory imaging. In the past ten days, he did not dive into the lake to complete it as he had done when he was cultivating before, but honestly stood on the hillside to complete it, and when he relaxed down, he found that his legs were already a little numb.

If it weren't for the fact that his cultivation had the skill of chasing the sun, which made his body strength far beyond that of ordinary cultivators, he would simply not be able to stand for nearly ten days without the blessing of spiritual energy. At this time, Tian Xu floated in the air, raised his legs high above his head, and massaged his numb legs with aura, only feeling extremely comfortable. After a while, he felt that the fatigue of his legs had recovered by six or seven percent, so he maintained the posture under his head and feet, spinning around in the air, and at the same time scanning the flowers and plants in the medicine king bucket with improved olfactory imaging, and he was in a very happy mood.

Turning the corner of the mountain, Tian Xu saw Ziyan standing on the big stone she used to practice, holding the spirit sword she didn't like to use, and there she simulated the movements of the three knives of Ku Ding in a gesture. Judging from the movements, what she is practicing now should be the second knife "Everything is Some", which is occasionally mixed with the first move "Finding Flaws and Gaps", and it seems that the first move "Finding Flaws and Gaps" She has already practiced well. As for the third move in Ku Ding's three knives, "hesitating and looking around", Tian Xu himself has not found that feeling, and he can't do it at all. Seeing that Ziyan was practicing seriously, he didn't bother, but after turning around, he flew to the surface of the lake, plunged into the lake, and swam freely in the water. At this time, he did not use the aura fairing and the propulsion formation, but relied on his breathing ability in the water and his physical strength to swim, fully feeling the encirclement of the water, and relaxing his body and spirit. Saying that the long-term spiritual perception and cultivation made him feel a little tired, and swimming as he wanted like this was the best way to relax his body and mind.

After swimming for a while, Tian Xu's spirit became more and more relaxed, and he slowly fell asleep.

In his sleep, Tian Xu dreamed that he came to the outside world and faced the siege of a group of Sainthood cultivators, with the help of the new olfactory imaging that he had just realized, he could see clearly the Immortal of the Sainthood Realm hidden around, but he pretended not to know, but instead launched a surprise attack on the other party when it was unexpected, killing the other party one by one, and he was so confused. In a moment of pride, I couldn't help laughing.

Laughing in the water, the water filled in his lungs was not as easy to be discharged as air, but it shook his chest with a faint pain, waking up Tian Xu, who was immersed in a sweet dream. He opened his eyes blankly, and after understanding the environment he was in, his mood was very depressed. He understood that he was unhappy because he didn't laugh enough happily, but there was still a layer of shadows lingering in his heart, and a question lingered in his heart for a long time: no matter how weak he was, the Sainthood Realm was also an earth immortal, how could he be killed by himself as easily as in a dream? Something must be wrong. If you meet the enemy in your current state, once the problem erupts in battle, your own life may be in danger.

Tian Xu carefully recalled the scene of the battle in his dream, but it was so real, if he looked at the effect of the olfactory imaging he had just improved, there was really such a possibility. Is there something wrong with that kind of olfactory imaging?

He checked the olfactory imaging from the principle to the experiment, and did not find anything wrong, but he was really relieved. This feeling is like that elusive intuition, telling him unequivocally that there must be a problem, and this feeling of danger will not deceive him! If he cannot find the problem, this hidden danger is like a legendary sword of Damocles, hanging over his head all the time, and he does not know when it will fall.