What is ferocious, Luo Tian finally saw it. Although the power of the magic cannon is very amazing, and although a large number of star insects have directly turned into powder, these are still not worth mentioning in the face www.biquge.info of the huge wave of star insects. A large number of dark blood rats fell, and the later dark blood rats directly devoured the corpses of their former companions, and then continued to pour towards the city wall.

In order to be able to successfully block the rat swarm, under the guidance of the unknown voice, the humans defending on the city wall have continuously pushed the battle line back, trying to exert the maximum power of the magic cannon. Once the Dark Blood Rats rush under the walls, even if the walls are a thousand meters high, they can rush over the walls.

In order to ensure a sufficient firing frequency, the optimal range of the magic cannon is 20 kilometers. A firing range of twenty kilometers guarantees a guided firing rate of three rounds per minute per magic cannon, or six unguided firing per minute. Ten seconds is already the design limit of the magic cannon, and it takes a while for the concentration of spiritual power and the activation of energy.

At the same time, the firing range of twenty kilometers is also a safe distance to the limit. Once the twenty kilometers are broken, the effects of the explosion of the magic cannon shells will affect the professionals defending the city walls, and the chaotic magic elements will even interfere with the spell casting process of the mages on the city walls.

In other words, once the Dark Blood Rat breaks through the twenty-kilometer line of defense, either the magic cannon will be replaced with a more low-level shell, or other means of defense will have to be resorted. However, compared to the magic cannon, other methods are obviously not so efficient, so the twenty-kilometer defense line can be kept as best as possible.

However, some things are indeed impossible to develop according to people's minds, even if the magic cannons on the city wall are only four hundred meters apart, even if they can fire six rounds in a minute, even if the reserve of cannonballs is still very sufficient, there are still many dark blood rats who have crossed the defense line and rushed straight to the city wall.

For these fish that slipped through the net, the method adopted by the students was to use the magic crystal cannon to shoot in a small area. Compared to the magic cannon's built-in channeling effect, the magic crystal cannon is more laborious to use. The operator of the magic crystal cannon, the relevant talents specially cultivated by the Tiansheng Academy, are quick enough to think quickly and react fast enough to quickly calculate the azimuth, angle and strength of the launch.

The effect of the magic crystal cannon is completely different from that of the magic cannon, the magic cannon is regarded as lifting the ground, and the magic crystal cannon is to dig holes in the ground. Although the ground of the battlefield space has been specially strengthened, it still cannot stop the bombardment of the two. The range of action of a third-level magic crystal projectile landing is about ten meters, although it cannot be compared with the one-hundred-meter radius of the third-level magic cannon, but it is still enough to sweep the remnants.

Time continued to pass like this, and the Dark Blood Rats continued to pour out of the stargate as if they were endless. The cadets defending on the city wall were already a little numb to this, they watched the dark blood rats surging like a tide, and saw them being constantly wiped out from their eyes by magic cannons, and no one could tell how many dark blood rats died at their hands.

However, except for Luo Tian, no one noticed that in the vast group of rats, there were some different dark blood rats. Luo Tian found that these special dark blood rats did not rely on their eyes, but on the induction of the energy core in their bodies. These suddenly appeared dark blood rats were not much different from ordinary blood rats in appearance, but the energy intensity in their bodies was more than five times that of ordinary blood rats.

This has also happened on Earth, and that is the so-called mutant star worm. However, these dark blood rats do not have mysterious runes similar to the earth, nor do they have so-called energy shields. For these variants of the Dark Blood Rat, Luo Tian didn't know more than the others present.

Luo Tian didn't specifically inform the others present that this kind of energy strength should not be able to cause any damage to the city wall, and let these variants of the Dark Blood Rat launch an attack to figure out their abilities. The ability of the star insect can be said to be strange, although it has some relationship with its genetic composition, but the relationship is not very absolute.

The Dark Rat's original strongest skill was to burrow, relying on its sharp teeth to burrow through the ground. After being transformed into a Dark Blood Rat, he did not have any ability to burrow. After seeing these mutated dark blood rats, Luo Tian seemed to have guessed something.

Sure enough, the mutated Dark Blood Rat's ability is indeed to make holes. The battlefield space has been strengthened by the star core consciousness, and some attributes such as strength have even reached the standard of sixth-level materials. This kind of ground is not easy to drill for the Dark Rat, but it is really not too easy for the mutated Dark Blood Rat.

Although the number of this newly emerged mutant dark blood rat is less than one percent of the total number, the specific number is still very staggering when put into the huge base. The speed at which the mutated dark blood rats burrow is even comparable to the speed of their counterparts on the ground, and what is even more deadly is that behind each mutant dark blood rat is a string of ordinary dark blood rats.

Luo Tian was not worried that those rats could directly drill through the city wall, the obsidian city wall ran through the entire space, and the ninth-level material was not something that these rats could bite. However, Luo Tian estimated that the students' defensive plan should be regarded as a failure, and it was not difficult for the dark blood rats sneaking underground to avoid the bombardment of the magic cannon on the ground.

In fact, even if the magic cannon can "scrape the ground", the depth is limited. The main purpose of strengthening the battlefield space was to prevent these attacks from causing excessive damage, but now this protection has become an umbrella for the Dark Blood Rats. At a depth of five meters underground, the magic robe could not be touched at all.

There are still capable people in the Heavenly Saint Academy, and after the Dark Blood Rat burrowed into the ground, someone discovered the anomaly on the battlefield. "Attention, there are rats that can burrow into the ground, and the magic crystal cannon also gives me a covering blow." It was still the mysterious voice, which had been directing the battle, but had never shown up.

Hearing this order, the students present gradually discovered the abnormality on the battlefield. The Dark Blood Rat's population is rapidly decreasing, and instead of being wiped out, they have all burrowed into the ground, leaving only a small hole in the ground. "Quick, fifteen kilometers, magic crystal cannon covering strike."

The order was rushed, and the reaction of the magic crystal cannon was also rapid. The maximum rate of fire of the magic crystal cannon can reach twenty rounds per minute, and all the magic crystal cannons on the city wall let out their own screams, smashing like raindrops in the area of about twenty kilometers.

After a loud roar, fountains of blood appeared on the ground, and bright red blood gushed out from these caverns. The speed at which this mutated dark blood rat drilled shocked everyone, and it was clear to everyone present that the twenty-kilometer defense line should be difficult to hold.