I become stronger by sacrificing my lifespan, becoming invincible in the world.

The patrol battalion's garrison was located right next to the western wall of the inner city of Guiku Pass.

Compared to the crooked and dilapidated mud houses of the scout camp, the barracks here are much neater, with uniform gray stone walls and black tile roofs. Although they also look old, at least they are not drafty or leaky.

The drill ground was made of compacted loess, with several worn-out wooden dummy stakes and stone weights placed along the edge. The air was less filled with the musty smell and despair of the previous day, and more with the solemnity unique to soldiers.

Lin Chen's new residence was a barracks shared by four people. Besides him, Zhao Tiegu, and Li Quezi, there was also an old soldier named Sun Cheng.

Sun Cheng was in his forties, taciturn, and had a claw mark on his left cheek that, even after healing, still looked ferocious. It was said to be left from an encounter with a demon wolf in his early years.

Seeing Lin Chen and the other two enter, he simply nodded and continued to polish his long spear, whose blade was gleaming.

"Brother Sun, please take care of me in the future." Zhao Tiegu took the initiative to speak, handing over a small piece of cured meat he had bought on the way.

Sun Cheng looked up at him, but didn't answer. He said in a low voice, "The rules of the patrol battalion are: talk less and observe more. Don't ask what you shouldn't ask, and don't touch what you shouldn't touch." After saying that, he lowered his head again.

Zhao Tiegu awkwardly withdrew his hand and exchanged a glance with Lin Chen and Li the Cripple.

After a quick settling-in, a messenger came to inform Lin Chen to go see the patrol battalion commander.

The squad leader, surnamed Wu, was a lean, dark-skinned middle-aged man with sharp eyes and large knuckles. He glanced at Zhang Heng's order and then looked Lin Chen up and down a few times.

"Lin Chen? Captain Zhang specifically instructed him."

Team Leader Wu's voice was hoarse as he said, "Since you've joined the patrol team, you have to follow their rules. The three of you will be assigned to the third squad of the Bing-character detachment. The squad leader is Sun Cheng, the one in his barracks. Sun Cheng will tell you about the daily patrol routes, passwords, and duty shifts."

He paused, then added, "The patrol team's job seems more secure than the scout battalion's, but you have to keep your eyes open. The area outside the pass isn't peaceful, and the area inside... isn't a monolithic entity either. Mind your own business, don't cause trouble, and most importantly, don't give anyone any leverage against you. Understand?"

"Understood." Lin Chen nodded.

"Go ahead, familiarize yourself with the duties today, and start your shifts tomorrow."

Back in the barracks, Sun Cheng had already cleaned his gun. Seeing the three men return, he got up, took a yellowed animal hide map from the wall, and spread it on the table.

"The defense zone of Bingsanwu," he pointed to the map, "is the west city wall, from the 'Wangbei' beacon tower to the 'Tiezha' arrow tower, with a total of twelve crenellations, about sixty zhang in length. Four people are on duty in shifts, two people per group, changing every four hours. The password is changed and issued by Captain Wu himself at Chenshi (7-9 AM) every day."

He speaks quickly, but his points are clear and logical.

"Patrol points: Observe the wilderness outside the pass for any unusual smoke, firelight, or large-scale animal movement; pay attention to any new damage or signs of vandalism on the city wall and crenellations; at night, be especially vigilant for signs of climbing and unusual sounds. In case of emergency, use whistles and beacon fires as signals."

Lin Chen carefully examined the map and silently memorized it.

Sun Cheng glanced at him, seemingly satisfied with his serious attitude.

"Besides guarding the city walls, every five days, we need to go out of the pass to patrol several fixed lookout points and trap areas within five miles of the defense zone. This is the most dangerous job; we have to use our eyes, ears, and nose."

Next, Sun Cheng explained the trivial matters such as weapon maintenance, handover procedures, and emergency signals.

Zhao Tiegu and Li Quezi had been in the scout camp for a long time and were familiar with these things, so they quickly memorized them.

In the evening, the cook brought dinner. The food in the patrol camp was indeed much better than that in the scout camp. Although it was the same porridge and mixed flour pancakes, at least there were some bits of meat in the porridge, and the pancakes weren't so hard that they were gritty.

The atmosphere in the barracks was silent during mealtime. Sun Cheng ate by himself, and went out to wash the dishes after he finished. Zhao Tiegu lowered his voice and said to Lin Chen, "This Sun Cheng is an old hand in the military, his skills should be quite good, but he has a cold personality."

Li the Cripple was somewhat worried: "That bastard Chen Hong, he definitely didn't have good intentions in putting us under Zhang Heng's command. This patrol battalion is probably not safe either."

Lin Chen didn't speak, but slowly chewed his biscuit. He knew Chen Hong's intention, of course: putting himself under Zhang Heng's watchful eye was both a temporary compromise and a way to plant a seed of trouble.

Next, Chen Hong will definitely try to create trouble for himself in the patrol battalion, or find an opportunity to get himself out again to "carry out a mission".

We must quickly establish ourselves here, gain Zhang Heng's trust, and at the same time... improve our strength.

As night deepened, the soft snores of Sun Cheng and Zhao Tiegu echoed through the barracks. Li the Cripple, still recovering from his injuries, slept restlessly, occasionally letting out suppressed groans.

Lin Chen sat cross-legged on the bed, not sleeping.

Consciousness sank into the divine jade.

[Current lifespan reserve: 48 years] (remaining after devouring the sand bandit leader and refining some of the feedback)

[Can evolve into the second move of "Blood Battle Blade Technique," "Blood Shadow Chain," requiring 120 years of lifespan; lifespan insufficient.]

[A deep repair of the dantian can be attempted (minor), requiring an 80-year lifespan, with a 30% success rate.]

[The basic archery technique "Wind Chasing Arrow" (incomplete) can be evolved, requiring 15 years of lifespan.]

My lifespan is almost gone again. Although I made some money in Blackrock City, most of it was used to refine the backlash and heal my wounds.

The Blood Shadow Chain technique cannot be evolved for the time being, and deep repair of the dantian is too risky. Archery, however... might be useful. Patrols require bows and crossbows, and good archery skills would significantly increase safety.

"Evolution of 'The Arrow of the Wind'"

[Evolution confirmed...consuming 15 years of lifespan...evolving...]

A slight burning sensation came from my chest, accompanied by fragmented techniques and muscle memory related to nocking the arrow, drawing the bow, aiming, and coordinating breathing, which slowly seeped into my consciousness.

It's not advanced archery, but the most basic yet practical battlefield shooting technique, emphasizing stability and accuracy.

A moment later, the evolution was complete.

[The evolution of "The Arrow of the Wind" (incomplete) is successful; proficiency level: beginner]

Lifespan Reserve: 33 years

better than nothing.

Lin Chen then tried to mobilize his lifespan to slowly nourish his body and repair the minor injuries left by today's journey and previous battles.

As lifespan slowly depletes, a comfortable warmth spreads through the body, like soaking in warm water.

The next day, at the end of the Yin hour (5 a.m.), while it was still dark, the piercing sound of copper bells rang out from the barracks.

Sun Cheng was the first to sit up, deftly donning his armor, sword, and bow.

Lin Chen and the other two quickly got up and organized their equipment.

The patrol battalion's leather armor was much better than the scout battalion's shoddy goods; it was made of tanned, hard cowhide, with iron plates attached to key parts, so it was acceptable.

The four men arrived at the "Wangbei" beacon tower on the west city wall and took over from the two soldiers on duty the previous shift.

The two men had sunken eyes and looked exhausted. After the handover, they hurriedly went down to the city to rest.

Sun Cheng and Lin Chen took the first shift. Zhao Tiegu and Li Quezi stayed in the hidden cave under the beacon tower to rest, and would rotate after four hours.

As dawn broke, standing atop the three-zhang-high city wall, the cold wind felt like a knife.

Beyond the pass lies an endless gray-brown wasteland, dotted with withered shrubs and exposed rocks, the distant horizon blurred and merging with the leaden sky.