Lu Heng did not truly raise Lin Yu's abilities to the absolute limit; in the apocalypse, these special ability attributes were sufficient as long as they were usable.
He subtly inquired among the base personnel who had arrived that day and learned that the highest known level outside was only seventh tier. Therefore, upgrading Lin Yu to level ten was more than enough.
Consuming demon crystals was significantly faster than consuming energy crystals for advancement. This was because the energy contained within demon crystals was far greater than that in energy crystals. Consequently, Lin Yu did not spend too much time reaching level ten.
After watching Lin Yu complete his advancement, Lu Heng took out several printed booklets from his space. "These are books obtained from another world. I've organized them all for you. Study them according to the descriptions here. If there's anything you don't understand, jot it down, and I'll help you ask about them collectively later.
After all, the learning system there is different from ours, and the study of these abilities in that world has existed for a long time. Much of their theoretical knowledge is also derived from practical experience. You can learn from them.
Also, these two books introduce the herbs and basic alchemy formulas of that world. Take a look at them. Your Netherworld Fire can not only kill zombies but also be used for refining pills. This is very rare. In that world, the Netherworld Fire is something that appears only once in ten thousand years."
"Is this difficult to learn?" Lin Yu glanced at the alchemy formula book.
"I don't know. You look at it first. Once you're familiar with it, I'll get you some herbs and an alchemy furnace."
There were no alchemy furnaces in his space. After all, Jinyang City only sold finished pills, and those alchemists would not come here to refine them.
Although Wu Chenzi had also come to Jinyang City, his alchemy furnace was either left at the Danyang Sect or placed in his own storage space. Lu Heng had also investigated and had not yet found any alchemy furnaces in his space.
"However, you should not go out to kill zombies for now. Once I'm done with my affairs in the other world, I'll take you out for training."
"Then, Brother Lu, what if someone comes to buy weapons?"
"If anyone comes, tell them that at the end of each month, I will be selling items in [Fallen City]. The city gates will only open on that day. If anyone causes trouble, let the Golden Eagle handle it."
Fortunately, he had acquired a flying Golden Eagle. Otherwise, he would have to open the city gates every time to let other mutated animals out, which would be quite troublesome.
"Okay," Lin Yu nodded. Today's gains were truly significant. However, Lu Heng had been accompanying him for his upgrade since around noon, and it was now well past dark. Lin Yu scratched his head and said a bit sheepishly, "Brother Lu, you should go rest too. I was so focused on upgrading just now that I forgot the time. I..."
"It's fine. Train well. Even though your current level in the apocalypse is almost unmatched, you must not forget that there's always someone better. Even if your strength is sufficient, you cannot neglect your daily practice.
Then I won't be resting here tonight. If there's anything, just have the Director call me. Oh, and don't always let the Director and the others watch shows. Watching too much of that is bad for the eyes."
Just as he was about to get up and leave, Lu Heng added another reminder.
Director, "When did we watch too much? You were busy before and didn't show us many shows."
Turtle, "That's right."
...
Returning to his space, Lu Heng went to sleep. After a day of activity, it was impossible not to feel tired.
Although he hadn't done much in the apocalypse, constantly expending energy was quite draining.
After a night's rest, Lu Heng's energy and spirit were restored, and he then remembered something very important.
After his last upgrade a few days ago, he hadn't yet thought to check if the remaining three directions for exiting the space city had also changed.
This was very important, as he needed to understand any changes within his space as early as possible.
With a thought, Lu Heng appeared at a road exit.
Lu Heng looked at the end of the road. There were no changes here; he still couldn't see the scene on the other side clearly.
Lu Heng then checked the recording equipment. The storage space on these devices was full, but reviewing the previous playback showed no changes.
After installing a new storage chip and checking the equipment's location, Lu Heng proceeded to the other road exits.
These two exits also showed no changes, which puzzled Lu Heng. After all, when his level increased, the spatial entrance leading to the Shen Yuan Continent, which was the first to change, always showed some differences after each upgrade.
But he had already upgraded to level twelve, so why were there no new changes to those three exits?
Never mind. He would go back, take a bath, and then see if Wu Chenzi had exchanged new types of demon crystals for him.
In fact, Lu Heng had six level-seven human crystals and over ten level-five human crystals in his space. Consuming these could also achieve the effect of upgrading, but Lu Heng was not willing to use them for the time being.
Since there were now substitute demon crystals available, Lu Heng genuinely did not want to use crystals taken from humans. It was a kind of instinctive repulsion.
However, while bathing, Lu Heng chuckled as he rubbed the "tattoos" on his body, thinking that he, a good youth from before the apocalypse, now had tattoos all over his body.
Also, since he had upgraded again, he could consider collecting some interesting magical beasts from the other world as his contracted pets.
After all, these contracted animals possessed strong combat abilities. Whether it was killing zombies or magical beasts, they could assist him or be used entirely for combat.
...
"Master, are you there?"
From outside the door, Lu Da Niu's voice could be heard. Lu Heng quickly changed his attire and returned to his room, then responded from within.
"I'm here. What is it?"
"Oh, Mr. Wu just arrived. I've already invited him into the shop in front."
"Alright, I'll be right there."
"Hahaha, Little Friend Lu, is the matter settled so quickly?" Wu Chenzi was making tea for himself. He looked up and smiled as he saw Lu Heng walking from the back hall.
"Yes, I returned as soon as the city gates opened this morning."
Lu Heng smoothed his robes and then sat down opposite Wu Chenzi.
"Come, have a cup of hot tea. The weather is getting a bit cold."
"These are the demon crystals exchanged for the crystals sold yesterday. I thought about exchanging for types you don't have here, as you suggested. However, the demon crystals that these people outside have are not of many varieties. After all, some types of magical beasts are inherently rare, which is normal. Please accept these first."
"Hmm, are the crystals enough for the exchange?"
"How could they not be? I also told them as you instructed, that these crystals are limited to a certain purchase amount each day, and no more. I told them to come back tomorrow."