"I asked them to build it." With the sound of words, a dwarf in a bearskin robe walked in front of Li Nan.

Seeing the arrival of Tyrion, the prime minister of the north appointed by himself, Li Nan jumped off the tall white wolf and asked with a smile, "You are no longer in Winterfell to deal with political affairs, why are you here?" ”

"I've arranged all the winter preparations in the north, and I heard that there will be a big war here, so I brought the captives of the Frey family and asked them to come and build the city wall."

Li Nan pointed to the two-hundred-meter-high Great Wall of Desperation and said with confidence: "Although there are millions of Alien Ghost Legions, I don't believe they can capture this wall of miracles. ”

"Bringing an umbrella on a cloudy day may be useless, but if you really have to face a heavy rain, you won't have to get wet. Besides, these Frey captives, since you don't want to kill them all, you have to feed them when you are idle, so it is always right to let them do some work and add some protection. ”

After listening to Tyrion's explanation, Li Nan nodded slightly in agreement, but he asked with some curiosity: "I see that the city wall you commanded is not too high, what is its purpose?" ”

"Of course it's useful, it's useless to say more, I'll let someone show you it."

Tyrion commanded several nearby generals, and soon the soldiers placed straw men in the corridor between the two walls to act as enemies, and a group of heavily armored cavalry armed with bayonets mounted and assembled.

These heavily armored cavalry formed a battle formation of five horsemen and galloped fiercely from a distance.

Most of the cavalry battles in this world use shock tactics. This tactic of shock cavalry was the first tactic employed by the Normans in southern Italy on earth, and no infantry could match it for the next four hundred years.

The secret of this tactic is that the cavalry has changed the way of fighting, and the cavalry is charged in a one-way way, the cavalry gun is clamped under the arm, and the horsepower is impacted, and the arm is released after the impact to facilitate the unloading, and the cavalry gun is basically disposable, and the advantage of this is that the full speed impact of the war horse plus the weight of the knight and the armor is converted into gravity acceleration and all concentrated at the tip of the cavalry lance, and this impact force is invincible for a long period of time.

Li Nan noticed that all the knights' riding spears under their arms were different from those he used in the martial arts competition, the tip of this kind of riding spear was made of metal, which was very sharp and sharp, coupled with the impact of the war horse, it was estimated that no matter what stood in front of them, it would be pierced and knocked away.

In this long corridor, which was not spacious, but it was extraordinarily flat, no enemy could stop the onslaught of the heavy cavalry, and when this powerful cavalry force swept by, the straw men who had been standing there were torn apart from the blades of grass fluttering in the sky.

Tyrion smiled smugly at Li Nan, "How is it, this way is okay, right?" ”

"Not bad!" Li Nan patted Tyrion's shoulder vigorously and praised excitedly: "It seems that I went to King's Landing to save you, what a correct decision!" ”

"Ahem, cough, cough......" Tyrion, who was slapped by Li Nan for coughing, hurriedly left him a few steps.

There were not many arms in the Seven Kingdoms, and they were generally divided into cavalry, infantry, and archers. And for the defense of the city, the cavalry that is the most lethal and has spent a lot of resources to train is not superior, and it is really a waste to let the cavalry give up their horses to fight a war of attrition to defend the city.

Tyrion's move was an insurance policy for the Northerners, and it also brought out the best in cavalry, and it seemed that this dwarf was indeed a talent.

In addition to charging the cavalry, the passage between the walls also had a role, and then Tyrion ordered someone to demonstrate it to Li Nan.

A bucket of wildfire was dumped in the corridor, and the green liquid quickly spread, and when the rocket ignited the wildfire on the ground, this section of the corridor burned into an unquenchable fire.

All this made Li Nan very satisfied, with these two means of defense, he who was originally going to face millions of walking corpses, and he had a little more confidence in his heart.

After communicating with the beast kings of the various races of the beast group, Li Nan divided the area for them, let them disperse their own groups to live in the dense jungles and mountains in the north, and formulated a code for them to gather.

A large number of carnivorous beasts have come to the north, although doing so is likely to bring disaster to some herbivorous groups, but the balance between nature and environment is not a priority for Li Nan now.

Once everything was taken care of, everyone gathered again in the Hall of Shields in Castle Black.

After Li Nan left, the others were not idle, the acting commander of the Night's Watch, Sir Thorne, and the Onion Knights, who had been training soldiers, and many of the scholars in the service of the nobles, led by Scholar Emon, rummaged through the books of each family to find a way to deal with the Alien Legions.

The hard work paid off, and after a lot of reading and searching, Aemon and the others really found a way to restrain the ghosts and ghouls in an ancient book.

Carefully looking at the black glass-like stone in his hand, Li Nan asked tentatively, "Is this obsidian?" ”

The blind Aemon University Scholar confirmed, "Yes, this is Obsidian, but it also has a name, Dragon Crystal. ”

With a slight effort, Li Nan broke the black stone into two pieces, so he asked with some suspicion: "This thing seems to be very brittle and fragile, can it really kill those strange ghosts?" ”

Scholar Aemon didn't answer Li Nan's words directly, but beckoned behind him, and several other scholars walked over with a box in their hands.

When the box was opened, it could be seen that it was a rotting and severed hand that was still violently moving, and at a glance, it was clear that it had been cut off from the ghoul.

Academician Aemon explained, "Because there was only one ghoul left, we didn't have much to test and had to cut the ghoul open. ”

No one would have sympathy for ghouls, and Li Nan didn't have any problem with the Bachelors' approach, he was now more concerned about whether Obsidian could kill this undead creature.

The obsidian that had just been broken formed an unusually sharp tip, and Li Nan stabbed it into the ghoul's rotten hand, only to see a dark red light glowing from the black stone, directly shattering the cold ghost hand.

Li Nan knew that obsidian was a natural glass formed by magma flowing out of volcanic lava and suddenly cooling, which did have something to do with flames, but he didn't expect that the obsidian in this world actually had such a special effect.

After field trials, it has been proven that obsidian has the effect of killing ghouls, so the question arises, where is the obsidian mine?

In this world, obsidian is not very useful for metal deposits such as gold, silver, copper, iron, etc., so there is no one to mine these useless things, so the average person really doesn't know where obsidian is.

But in the southwest corner of Westeros, under the rule of the Riverbend Kingdom, there is a neutral place called Oldtown, where there is a school town.

The school city is a complex of buildings in the Old Town, and is the supreme governing body of the scholars of the Seven Kingdoms. It is here that they meet, study and train newcomers. The school town is also the residence of university scholars.

Scholars were a strange group of scholars, scientists, explorers, chroniclers of history, and erudite advisors to the aristocracy. Sometimes, they are also researchers in the occult who pretend to be pious.

Scholar Aemon's reputation in the school city was very high, so when he sent a letter of help with the precious white raven, the whole school city was busy.

Thanks to the efforts of the entire school, all the scholars began to look through the various collections of books for thousands of years in the world's largest library, and finally found the place where the obsidian was produced.

No one is more familiar with this place than The Onion Knight, as it is the domain of Stannis, the king of the Narrow Sea--- Dragonstone.