As a poor student, Greta couldn't explain the origin of gray fog, but the harm to gray fog was clearly understood.

The essence of gray fog is actually some high concentration of energy, but these energy is very violent and cannot be absorbed, and will cause harm to humans and elves. Therefore, except for powerful professionals, ordinary people rarely walk out of the city and enter gray fog.

Speaking of gray fog, we have to talk about the "special products" of gray fog, a violent alien beast.

For humans and elves, gray fog is a forbidden area for death, but for violent alien beasts, gray fog is like its hometown. In the gray fog, violent alien beasts will continue to recover their physical strength and heal their injuries. They are like the undead Xiaoqiang, and come and go like the wind, without any trace. Even the most powerful professionals are unwilling to provoke these violent alien beasts in the gray fog.

Of course, the main reason is that after killing these violent beasts, there is no benefit at all.

No one knows whether the organs and structures of these violent beasts are useful, but what everyone knows is that once the violent beast is killed, the corpse of the violent beast will begin to fog and decompose, and eventually become a pure gray mist.

Only then did Sawy understand why those people dared not approach him, and why Carloth pulled him away from his "trophy". It turned out that the corpse of the black beast was not a trophy at all, but a self-destructive bomb!

However, there are also strengths and weaknesses among the violent alien beasts, and the weakest ones are called gray beasts. Although these gray beasts are weak in strength, their body colors will blend into gray fog, and most of them will move in groups, which is the most troublesome.

The more powerful violent beasts will slowly change their bodies to black, so they are called black beasts. Although these black beasts are strong, their body colors are different from those of the environment. Most of them are lone heroes, and the degree of threat is almost the same as those of gray beasts.

The higher ones are high-level black beasts with pure black body color, as well as more powerful super-level black beasts and violent black beasts, but Greta doesn't know what they look like and what their characteristics are.

If this is the case alone, gray fog and violent beasts will not be worthy of such a headache. The real terrifying part of gray fog and violent beasts is their reproduction speed and the black tide that is almost once a year.

For example, the previous black beast wolf vulture, whose scientific name was the ox-horned bone-bone wolf vulture. If a wolf vulture migrates to the vicinity of Qingyan, then in a few years, nearly a hundred wolf vultures will appear near Qingyan!

According to scholars in Xuecheng, the way these violent beasts reproduce is to split and proliferate. When a violent beast grows to a certain stage, a small part will be split from the body and redevelop into a new violent beast. Moreover, the stronger the violent beast, the more it will split.

For example, when the wolf vulture killed by Sawyer grows to the split stage, it can split out three to seven juvenile wolf vultures at one time, while most ordinary gray beasts can only split out one juvenile at a time.

Of course, the stronger the violent beast grows longer and the fewer the times it splits. For example, ordinary gray beasts only take one month to half a year from the juvenile body to the division stage, and then they can split at least ten times, while wolf vultures take two years to grow to the division stage, and most wolf vultures can only split two to three times in their lifetime.

Even so, the proliferation speed of the violent beasts is enough to cause headaches for humans and elves.

When the violent beasts within a certain range of the city tower reach a certain density, the violent beasts will spontaneously impact the tower and form a beast tide. Because countless violent beasts gather in the gray fog, they look like black tide, and for all other reasons, they are also called black tide.

The city where the Kuroshima occurs most frequently is naturally the Central Ring Road City, which is as high as the 17th Ring Road. The city's towers are the most powerful, with the widest shelter and the widest influence. At least three Kuroshimas occur every year, and the duration of each Kuroshima is more than one month. In other words, at least one-quarter of the time of the Central Ring Road City deals with Kuroshima every year.

In the Sapphire Ring City located in the north of the mainland, the frequency of dark tide occurs once a year, and the duration is generally between half a month and one month. The interval between two dark tides is as long as one year, as short as ten months, and on average it is exactly once a year.

This is also the case in other cities. Basically, the smaller the city, the fewer the rings, the lower the frequency of the black tide, and the smaller the scale. For example, in some small towns on the two and three rings, beast tide may not occur once every four or five years. Gray fog strongholds like Qingyan, because there is no tower, will not even cause beast tide. They just need to build the house stronger and then hide at home when the black tide occurs in the blue city.

At the same time, the occurrence law of the black tide also defines the distribution law of cities. In the high tower radiation range to large cities such as Blue City, there must be no other cities. However, outside the high tower radiation range of large cities, most of the small rings are interdependent and two or three rings are joined forces to resist the impact of the beast tide.

On the contrary, gray fog strongholds like Qingyan are just the opposite. A large part of them exist within the radiation range of the towers of the large ring city. On the contrary, few gray fog strongholds are attached to small ring city cities.

Of course, more gray fog strongholds are outside the radiation range of the tower. It is not that these gray fog strongholds do not want to rely on the protection of the ring city, but are too far away from the ring city to break through the blockade of gray fog for migration. The experts of the ring city find it difficult to search for the existence of gray fog strongholds in the gray fog. To put it bluntly, let alone these uncertain locations of gray fog strongholds, even gray fog strongholds like Qingyan, which rely on the protection of the ring city and are marked on the map, are difficult to find in gray fog. Unless this gray fog stronghold has important output, the ring city will establish a gray fog channel between the city and the stronghold.

As for what the gray fog passage is...

Miss Greta still said honestly that she forgot.

Sawyer was also helpless. Greta was the most "learning" person in Qingyan. This was because when she was a child, Greta's father Carlot asked a passing knight to take her to Blue City to study. However, the other Qingyan people were not even at the distant Blue City. Ninety percent of the people had never been to other gray fog strongholds around!

"It seems that if you want to continue to understand this world, you can only go to Blue City first."

Sawyer sighed, then looked at the girl who was holding her cheeks and waving her legs: "Greta, can you take me to Blue City?"

"No! I won't go!"
Chapter completed!