After successfully refining the three-grade rune, and the proficiency level was already very high, at this time, Yun Tian began to focus on the four-grade rune.

Although they are all things that can be refined by a two-star rune master, the four-grade rune is a heaven and a earth compared to the three-grade rune, you must know that the four-grade rune is a red paper rune, which is equivalent to something that spans a generation, and its power and quality are far from being comparable to the three-grade rune.

It is for this reason that the two-star rune master is a relatively special level, and unlike other professions, in the first vein of the rune, there will be a great difference in the identity of the same two-star rune master, and the difference lies in the refining ability of the three-grade rune and the four-grade rune.

If it is a two-star rune master who can only refine a three-grade rune, although it will be respected by people, it will not be worshipped, but a two-star rune master who can refine a four-grade rune can be respected by people, and there is a more important point, that is, a two-star rune master who can refine a four-star rune is very likely to break through to a three-star rune master, and those two-star rune masters who can refine a three-grade rune, the vast majority of them can only stop at the level of a two-star rune master for the rest of their lives and cannot advance an inch.

If it is said that the cultivation of martial arts is full of difficulties at every level, then the promotion of Fu Gong masters, alchemists, and array mages is even more difficult, because martial arts are the largest group in this world, they can communicate with each other, a large number of martial arts cultivation, accumulate a large number of materials, exchange with each other, communicate with each other, and promote the development of martial arts to the extreme.

On the other hand, the groups of Fu Masters, Alchemists, and Array Mages are often extremely scarce in number, and the materials required are also quite scarce, which makes it very difficult for them to improve, and every step they take, requires a lot of patience and effort.

However, although these auxiliary cultivators are very difficult, after all, compared to the strength of individual martial cultivators, this kind of thing is more attractive to all kinds of forces, so often these talisman masters, alchemists, and array mages will be respected much higher than those ordinary martial cultivators, and they can also get more benefits. Even in the conflict of different forces, often these talisman masters, alchemists, and array mages are the objects of focus, and few people will easily kill them, which makes this type of people live a very stable life.

Although every martial cultivator pursues martial arts, no one wants to hang up easily, everyone hopes that they can enjoy these benefits while being able to obtain benefits, so becoming a talisman master, alchemist, and array mage is also the dream of most martial cultivators.

The conditions for becoming a talisman master, alchemist, and array mage are very harsh, which limits this group to be a small circle.

After a previous trial, Yun Tian felt that his talisman refining level should have reached a high point, and he could continue to break through upwards, so he made this attempt.

At this time, it was late at night, and Yang Sanliang didn't come over to disturb him over there, so Yun Tian was able to calm down and concentrate on trying to break through the four-grade talisman.

When it comes to the four-grade rune, Yuntian is not trying to focus on the spirit gathering rune, because the structure of the spirit gathering rune is too simple, although it can also be upgraded to a higher level, but if it is blindly tried to refine the spirit gathering rune, it is likely to make it difficult for him to find some problems with the high-level rune, and it will also make Yuntian miss some valuable experience accumulation opportunities.

Because of this, the four-grade rune refined by Yuntian directly chose the more difficult thunder rune. Speaking of which, this thunder talisman is not simple, it is the most powerful of the four runes, and it has the characteristics of breaking barriers and killing at the same time, and because of its large killing range, it is a huge threat to strong enemies.

However, there is a difficulty in the refining of thunder runes, that is, the power of thunder and lightning needs to be injected, and the power of thunder and lightning needs to be either collected from nature or injected with thunder attribute martial arts.

But in reality, there are almost no martial cultivators who practice the true qi of the thunder system, so although the thunder rune is powerful, it is extremely rare.

Yuntian himself has the space to know the sea, and it is naturally not difficult to collect the thunder system true qi, and he likes the great power of the thunder system true qi, especially the effect of the leapfrog battle is remarkable, I believe that once this thing is made, it will definitely cause a sensation, since it is to be done, it must be a high-quality product, there is no need to repeat it at a low level, this is the principle of Yuntian.

The thunder rune is similar to the refining procedure of other runes, but there is an extra thunder injection, that is, the injection of thunder true qi, this process is extremely dangerous, according to records, even if it is the owner of the thunder true qi, someone has been killed when testing the thunder rune. Therefore, we must be cautious in this process, and it is precisely because the difficulty of refining thunder runes is far greater than that of other runes, so the price of this kind of runes is also many times more expensive than similar runes.

The materials required for the thunder rune are not much, but they are a little harsh, and even the red rune paper used for it is not an ordinary red rune paper, but a special silk paper, which is a kind of silk cloth to put it bluntly, but its texture characteristics are quite similar to paper. And it has to be soaked in the warm water of the lightning strike wood root for more than a month, but this process is not as long as possible, if the time is too long, the red silk rune paper will be rotten.

In addition to the red silk rune paper soaked in lightning root water, cinnabar should be mixed with star sand, which can accumulate all kinds of true qi, and can also accumulate thunder true qi, mix it into cinnabar, grind and soak, and then smear it on the surface of the red silk rune paper by drawing the rune, so that the drawn rune and the red silk rune paper are more suitable.

Previously, Yuntian had prepared some red silk rune paper soaked in lightning strike wood and placed it in the Zhihai space for a while, although this time was very short, but in the environment of the Zhihai space, Xingsha and the red silk rune paper were well integrated. And Yun Tian also believes that he has a strong spiritual sense, and the thunder true qi he injected for a while is from the sea of knowledge space, and he has a wonderful connection, even in the sea of knowledge space, Yun Tian has already felt that whenever the wind and clouds in the sea of knowledge space are thunderous, these red silk cloths soaked in the water of the lightning strike wood roots are already ready to move, which also makes him overjoyed, since he has such a strong perception, it means that the red silk cloth will definitely not repel the subsequent thunder system true qi injection, which is the goal that many talisman masters dream of aspiring to achieve。

Spreading out the red silk rune paper, Yun Tian took out a rune pen made of lightning strike wood, clicked on the cinnabar, and began to raise his hand to draw the composition of the formation.

The composition of the formation on the thunder talisman is also very delicate and complex, this is because the more exquisitely the formation is drawn, the more thunder true qi that attracts and accumulates thunder and lightning true qi later, the greater its power will naturally be, and a large part of the power of the talisman is reflected in this difference.

For the formation, Yun Tian is very proficient, because of this, he can also master the miniature formation depicted on the red silk rune paper smoothly, so under the wave of Yun Tian's letter, within a moment, the spell on a red rune paper has been drawn.