Battle for Northern Frontier: The game begins with the grassland woman buying him.

"What a brilliant scheme of using one wolf to devour another! Su Zhan is the knife, and Wang Ting is the hand that wields it."

They want to see me and Stone City fight to the death, then they can take over the entire North.

He abruptly raised his head, his eyes flashing with golden light, and swept his gaze across the silent generals and civil officials below the steps: "A clever diversion, excellent. Su Zhan is ruthless, and Wang Ting is vicious!"

He stood up abruptly, his heavy steps landing on the stone ground, and roared, "Seal all the city gates completely with stone slabs and molten iron!"

Pile all the movable boulders and logs onto the city walls! As for the granaries and water sources, send your most trusted guards, one post every ten steps, one sentry every five steps, keep a close watch on them. Anyone who dares to approach will be killed on sight! From now on, Wolf's Den Fortress is only for entry, not exit. We'll wait here for Su Zhan to come and chew this tough nut!

"I'll see if his teeth are harder, or my stone is harder! He thinks he can use me, Black Wolf God, as a stepping stone for the royal court? Keep dreaming!"

The order was given instantly, and the entire Wolf's Den erupted in excitement.

Driven by madness and despair, everyone roared and used all their strength to push the heavy stone blocks, blocking the city gate passage.

The blacksmith's furnace burned day and night, pouring molten iron into the gaps of the city gates and key points.

The walls were piled high with stones and logs, and behind the crenellations, every pair of eyes revealed exhaustion and barely concealed fear.

Looking at the grassland outside the city shrouded in a leaden gray sky, Su Zhan's army seemed like a shadow pressing down on everyone's hearts.

Inside the central command tent of the Stone Fortress outside the city, the atmosphere was completely different from the despair at Wolf's Lair.

The brazier was burning brightly, dispelling some of the chill of the north.

A huge sand table occupied the center of the tent, with Wolf's Den and the surrounding mountains, rivers, and possible underground tunnel entrances all meticulously marked.

Su Zhan, Bai Zhanqiu, Halbala, Chen Bao, Li Ergou, and Zhu Yeqing, who had just rushed back from his journey, gathered around the sand table.

Li Ergou's face still bore the stains left by his disguise, but his eyes shone with an alarming brightness as he pointed to an inconspicuous thin line behind Wolf's Den on the sand table, saying, "Third Master, Second Master, it's confirmed. Wolf's Den's lifeline lies in this underground river!"

His finger pointed to a secluded spot on a steep cliff behind Wolf's Den: "The entrance is extremely well hidden, concealed by a natural waterfall, and is usually difficult to find."

The water flowed swiftly and was icy cold. The interior was winding and deep, with many branching paths, like a maze. However, there was a main waterway that led directly to the reservoir inside the fortress and several hidden water cellars.

This is the Black Wolf God's last resort, and our only chance.

Zhu Yeqing added, "The situation inside the fortress is also bad. The Black Wolf God has given a death order, completely sealing all the city gates, using molten iron to reinforce all the gaps, and treating the stored food and water as if they were his lifeblood."

If we launch a direct attack, the cost will be enormous.

They clearly intend to drag us into a brutal war of attrition, until the royal court intervenes, or until our supplies run out.

Upon hearing this, Chen Bao punched the edge of the sand table, causing the model to shake slightly.

Blood seeped through the bandages on his shoulder again: "That old dog has retreated into his turtle shell! Second Boss, let me lead the Batian Gang brothers to the front lines. Even if it costs lives, I'll tear a hole in his wall!"

The hatred of the Wild Valley Gang and the devastating victory in Blackrock City filled this young general with a destructive power like a madman, and also with a hint of desperate urgency.

Su Zhan's gaze was sharp as an eagle's, sweeping over everyone before finally settling on the thin line on the sand table that represented the underground river.

He did not respond to Chen Bao immediately, but looked at Bai Zhanqiu: "Second Master, the casualties from a direct assault are too high, which is not what we want to see."

Moreover, Wolf's Den Fortress is a fortified and extremely difficult city to conquer, and the Black Wolf God is determined to fight to the death. If we insist on confronting them head-on, we will suffer heavy losses, which is exactly what he and the royal court want.

Bai Zhanqiu's eyes were deep. After a moment of contemplation, he slowly said, "Our best strategy is to surround their city and cut off their food and water supply. However, the royal court's movements are very urgent, and we don't have much time left."

Even a cornered beast like Black Wolf God will fight on. It's not impossible that the food stored in the fortress can last for a month. We can't afford to waste time.

And this underground river is indeed the key to breaking the deadlock.

He turned his gaze to Li Ergou: "Ergou, you've scouted the waterway. What's the situation inside? Can men and horses pass through? What's the strength of the defenses?"

Li Ergou's expression was solemn: "Second Master, although the entrance to the waterway is hidden, it is extremely difficult to travel inside."

The impact of the waterfall's cascade is so great that it is difficult for anyone other than someone with exceptional swimming skills and physical strength to swim upstream.

In some narrow sections of the waterway, only one person can pass sideways, and there are numerous undercurrents and whirlpools, with the water temperature being icy cold.

Most importantly, there are natural caves and branching paths inside, making it very easy to get lost if we go in.

As for the guards, no obvious guards were found at the entrance, but there must be heavy guards near the reservoir inside the fortress. This is their weak point, and they cannot afford to be careless.

In other words, this is a perilous path, a dead end, possibly the only way out, and of course, the only way to survive.

Su Zhan's voice was calm and steady: "We cannot afford to keep our army bogged down at the city walls. This battle must be won quickly."

He pointed to the sand table: "Chen Bao!"

"Your subordinate is here!" Chen Bao straightened his blood-stained chest.

"At dawn tomorrow, you will lead the main force of the Overlord Gang and two thousand infantrymen, carrying siege equipment, to launch a fierce attack on the south gate of Wolf's Den Fortress."

"The momentum must be immense, the offensive fierce, displaying an attitude of charging at all costs. I want all of Black Wolf God's attention and forces locked on the south of the city."

"Understood!" Chen Bao replied without hesitation, his eyes gleaming with the flames of revenge.

"Harbala!"

"Your subordinate is here!" Halbala bowed and said calmly.

"You will lead your Black Feather Cavalry to patrol the east and west flanks of the city. Once the city's defenders are mobilized due to Chen Bao's fierce attack, creating weak points, you can use mounted archery to harass and restrain them, create chaos, and disperse their forces."

"Yes, sir!" Halbala's eyes gleamed.

"Li Ergou!" Su Zhan's gaze turned to this fierce general.

"Your subordinate is here!" Li Ergou's spirits lifted.

"I'll give you one hour to select 100 of the most elite brothers who are best at swimming and holding their breath, and who are both brave and careful. They must be the best swimmers and not afraid of death."

Bring along a canister of kerosene, a dagger, a crowbar, a fire starter, and a sedative smoke made with Venom.

You personally lead the team and dive in at midnight from the entrance of the waterway behind the waterfall.

Your mission is as follows: First, find the main road leading to the reservoir inside the fort; second, eliminate any hidden sentries you may encounter along the way; third, upon reaching the reservoir or other sluice gates, release a large amount of hypnotic smoke to pollute the water source, create as much chaos as possible, and damage the sluice gates; fourth, wait for the signal, and then, in coordination with the outside, open a marked, abandoned small door near the west gate that is blocked from the inside.

Remember, your operation is secret; it's the key to victory or defeat. Once you infiltrate, there's no turning back. You must succeed!

"This humble general swears to complete the mission to the death!" Li Ergou's voice was resolute, his eyes flashing with determination.

He knew this would be the most dangerous and crucial surprise attack in Stone City's history.

Finally, Su Zhan's gaze fell on Bai Zhanqiu.

"Second Boss, I will personally lead the main force of the central army and the Iron Pagoda, and lie in ambush outside the West Gate. Once Li Ergou gives the signal or chaos breaks out at the West Gate, we can launch a general attack."

The Ironclad Cavalry will become the spark that ignites the breaching of the city.

"Good!" Bai Zhanqiu nodded emphatically. "Attack from both inside and outside, combine fire and water, and this Wolf Den Fortress will be the burial place of the Black Wolf God."

I am stationed at the central command, coordinating all parties to ensure the safety of provisions and supplies, and closely monitoring the movements of the Northern Royal Court.

With the strategy set, the war machine began to operate at high speed, and the camp was brightly lit with torches.

Chen Bao rallied the remaining members of the Batian Gang and their tribes for a final mobilization and preparation before the siege.

The air was thick with a sense of desolation and tragedy.

Albala's Black Feather Riders disappeared into the night sky.

Li Ergou, in a secluded tent, scanned the 100 selected assassins with piercing eyes.

Most of them were old clans who had started their businesses in Stone City, and there were also men from the wild ancient tribes who were excellent swimmers. Each of them had a resolute face and a calm look in their eyes. They had already written their wills and drank the strong liquor in one gulp.

"Brothers," Li Ergou's voice wasn't loud, but it clearly reached everyone's ears, "ahead lies an icy hell, a place of near-death experiences, but the day the fortress falls will be the day we achieve our greatest victory."

For Stone City, for our fallen comrades, for the foothold of us Han people on the grasslands, come with me to the gates of hell, do you dare?

"Dare!" One hundred composed figures converged into a powerful force, bringing the atmosphere inside the tent to its peak.

At midnight, all was quiet except for the howling of the cold wind on the desolate plain.

The massive waterfall behind Wolf's Lair concealed everything in its white cascade.

Behind the waterfall's curtain of water, a very hidden, slippery, moss-covered rock crevice is the entrance to the underground river.

The icy river water instantly submerged Li Ergou and the others; the immense water pressure and deafening roar from the waterfall were almost suffocating.

The water flowed swiftly and was icy cold, like steel needles piercing the bone marrow.

Li Ergou made a gesture, and 100 warriors, biting on specially made hollow reeds, took a deep breath and, like fish struggling against the rapid current, plunged into the dark tunnel.

Inside was a true underworld, so dark and thick that it was impossible to escape, with only the faint light occasionally filtering through the rock walls, reflecting shimmering ghostly flames on the water's surface.

The water surged and crashed between the narrow, twisting rock walls, producing a dull echo.

There are numerous forks in the road, and without the map provided by Zhu Yeqing and Li Ergou's exceptional sense of direction and memory, it would be easy to get lost in this natural maze.

They could only rely on their sense of touch and a faint sense of direction to struggle through the icy, narrow waterways.

The stone walls were slippery and sharp, and people were often swept up by the undercurrent and crashed into them, their muffled sounds swallowed by the water, before disappearing without a trace.

Their breath-holding time had reached its limit, and their lungs were burning with pain. Only their unwavering willpower supported them as they moved forward step by step. The short knives in their hands were not only weapons, but also tools for probing and securing their bodies.

After an unknown amount of time, as if traversing a long time tunnel, the sound of the flowing water ahead seemed to have changed slightly. It was no longer a simple gushing sound, but was mixed with a kind of dull mechanical sound.

Li Ergou's heart tightened, and he signaled everyone to slow down and be more discreet.

He groped his way out and, with the help of a sliver of light filtering through a crevice in the rock wall at the confluence of a larger waterway, saw the scene before him.

The waterway suddenly widens here, forming a deep underground pool. The pool is deep and connects to several wider waterways.

A massive wooden and stone sluice gate stands prominently beside the pool. The gate is heavy and controlled by a winch and iron chains, clearly a key node for regulating the water flow to the reservoir inside the fortress.

What made Li Ergou's pupils shrink even more was that on the stone platform next to the sluice gate, two guards wearing fur coats were sitting, looking somewhat drowsy, hugging their swords and spears and huddling together for warmth.

Their very existence is a huge threat.

A cold glint flashed in Li Ergou's eyes; he couldn't afford any mistakes.

He silently submerged underwater and gestured to his trusted men who were following closely behind, instructing them to take care of the guards.

Several of the best swimmers and most agile assassins immediately understood and then silently swam over like water ghosts.

Their movements were extremely careful, and the surface of the water barely produced any visible ripples.

A moment later, two very faint groans came from beside the sluice gate, followed by the soft splash of a heavy object falling into the water. The two guards were dragged into the deep pool without a sound.

Li Ergou quickly led his men to the surface. After climbing onto the stone platform and confirming that the guards had been dealt with, he immediately ordered his men: "Quick! Tie the sleeping powder and straw bags to stones and sink them into the main waterway of the reservoir. Sink several bags! Pour the remaining water and oil cans onto the wooden structure of the sluice gate, especially the winch and chains! The rest of you, follow me to find that abandoned west gate!"

The assassins immediately sprang into action, dropping specially made waterproof drug packets into the depths of the water. The packets would slowly dissolve with the current, releasing potent sedative components that would contaminate the water source.

The kerosene was carefully poured at the critical point.

Meanwhile, Li Ergou, referring to the map, led more than 20 people up the mountain along a more hidden, dusty, and cobweb-covered abandoned waterway.

This tunnel has long since dried up; it was an engineering passage left over from the construction of Wolf's Lair.

The exit was located in a dead corner inside the west gate, where debris was piled up. It was blocked from the outside by huge stone blocks, but the internal structure was relatively fragile.

Just as they were working intently, a wary voice suddenly came from the darkness of the abandoned passageway above: "Who goes there?"

Then the flickering light of the torches drew closer.

It turned out that the area was not completely unguarded; a patrol of three men had heard the strange noise and had come over.

"We've been exposed! Kill!" Li Ergou roared without hesitation and charged forward with his sword drawn.

In a narrow encounter, the brave prevail. The assassins behind him followed closely like cheetahs. A brief battle erupted in the darkness, with blades flashing in the torchlight, muffled groans, and then the sound of bodies falling to the ground, all of which were particularly clear in the enclosed passage.

The three patrolmen were quickly dealt with, and the last soldier used all his strength to blow the sharp bone whistle hanging on his chest before he died.

"beep--!"

The piercing whistle, like the howl of a ghost, tore through the deathly silence of the underground world, penetrating the thick layers of rock and faintly reaching the surface.

"Damn it!" Li Ergou's expression changed drastically. "Quick! Light the oil immediately, send a signal, and storm the small door!"