A puddle of leaking venom flowed down the cracks in the alchemy technology facility into the trench area of Zu'an, and accumulated into a puddle in an isolated pit in the depths.

Despite his humble origins, Zach has grown from a cloud of obscure slime to a thinking entity that inhabits the city's pipes, making occasional appearances to help the helpless, or repairing various public facilities in Zaun.

The first to spot Zach were a group of Zaan's children. They were playing in the puddle in the ditch when they noticed that some stones had been thrown back.

As a result, this "return pool" spread among the residents of Zu'an Digou, and finally attracted the attention of an alchemy technology cabal. Despite the objections of the local population, the group of alchemists pumped out the liquid from the pool and put it in a bucket and brought it back to their laboratory.

The alchemists devised various experiments to test the effects of negative and positive stimuli, and they found that there was a gelatinous mass in the pool, which seemed to have some kind of spiritual tendency.

Simply put, it mimics the type of stimuli it receives. If he is kind and loving, he will respond with childlike joy and playfulness.

However, if it is inflicted pain and irritation, the alchemists will have to sacrifice a large number of prosthetic-enhanced trench scavengers in response to the devastating reactions that follow.

Most alchemists thought that these reactions were mere nerve reflexes, but two of them weren't quite sure.

They questioned the ethics of these experiments, as if the purpose of the experiments was solely to create an incredibly aggressive creature. The two conducted an in-depth investigation and found that the entire project was funded by Saito Takeda.

He is a hot-tempered alchemy baron who is notorious for his bloody gang fights. The clue is clear: Takeda wants to develop a fighter who is not afraid of death, with a shapeable body, pervasive, and obedient. They also discovered the project's true name, the Zuan Amorphous Combat Body, abbreviated as ZAC.

The two begin to think about what to do, during which time they discover that the glue is not only a mimicry of a response to irritants.

They observed autonomous behavior when not receiving obvious stimuli – very similar to sentient organisms. They referred to the creature simply as Zach, and assumed that the behavior he exhibited indicated that he was a thinking and sentient entity.

They reported their findings to the head of the research team, but the stilt-like officer ignored their concerns.

Unwilling to give up, the duo began to carry out their own covert operations, trying to counteract the violent teachings given by the other team members.

They wanted Zach to tell the difference between right and wrong, so they let him experience first-hand self-sacrifice and generosity. Their efforts paid off, and Zach was saddened when he saw the researcher hurt his hand.

He was upset when he saw another researcher kill a rat in the lab. Eventually, the two of them had enough of the brutal experiments that other alchemists had done on Zack.

That night, which coincided with Zaun's Evolution Day memorial, the lab was empty, and they took the opportunity to dump Zach into a waste tank cart and drag him to a remote corner of Zaun.

Their actions were soon revealed, and Baron Takeda's soldiers began a search. But Zaun was big enough for the two researchers to get out of the limelight.

They had considered releasing Zach into the wild, but Zach didn't want to be released because he already considered the two researchers his family.

The two of them are the only ones in the world who are good to him, so he wants to learn more from them. In fact, the duo was extremely pleased with Zach's reaction, as they also liked Zach and even regarded him as their adopted son.

In order to evade Takeda's men, they changed their identities and appearances, and settled in remote trench areas, away from surveillance and spying. Zach learned to mimic their voices, and soon learned to morph his own colloidal clumps into the organs needed to make sounds.

He lived with his adoptive parents for many years, hiding in a pool of ditches or in a crack in a rock wall when necessary. Zack's "parents" told him about the world he lived in, telling him that there was a beautiful, magnificent side to the world.

They took him to watch the moonrise at the Gate of the Sun, the rainbow on the stained-glass canopy of the Zuan Exchange, and the bustling and vibrant beauty of the city center.

They also tell him that there is a cruel and harsh side to the world, and that Zach begins to understand that sometimes people can become vicious, ruthless, resentful, and prejudiced.

Zach rejects this behavior and helps his parents as much as he can, using his skills to benefit the surrounding residents while trying not to attract unwanted attention.

They did everything they could to heal the sick, repair machinery, and anything else alchemical knowledge could play a positive role. Those years are Zach's fondest memories.

He roams around the city of Zuan, with a near-never-ending network system and cracks in the foundation rocks as his exclusive access.

Although Zach has an independent sense of self, if the stimuli of his surroundings are too strong, his feelings may be submerged, temporarily absorbing the dominant emotions around him, with good or bad consequences.

Many times he was unable to control his impulses to help those who were oppressed and bullied, and to fight against the bullying street bullies. So Zuan gradually began to spread rumors about him.

While most of the rumors are stories about his helpfulness, there are also some that blame Zach for some devastating accidents, such as the destruction of a certain factory, or the tearing out of a large hole in a certain gutter residential area.

Eventually, these rumors finally reached Takeda Saito's ears, and he sent a group of prosthetic-enhanced villains to recover what he believed to be his own.

Because his alchemists have been trying to replicate the process of Zack's birth with the liquid left in the container, but it has always been in vain. So Baron Takeda was desperate to find the creature, so his men surrounded the house of Zack's parents and launched an attack.

The two of them rose up to resist, after all, they were alchemy technology researchers, how could they not have some secret weapons for self-defense, but their resistance could not last forever. In the end, the mob killed Baron Takeda, despite Baron Takeda's order to be captured alive.

At that time, Zack was exploring the rock crevices under the city of Zuan, but suddenly felt that his parents were in danger, so he rushed home along the pipe network to rescue him.

But it was already too late. He was furious at the sight of his parents' corpses, and the baron's men had never seen such a formation. Zach unleashed a ferocious attack, unleashing a variety of stretching, ramming, and heavy pressure techniques.

In his mixed rage, he destroyed dozens of houses in the surrounding area, and by the time the battle was over, none of the prosthetic-enhanced thugs had been left alive. As the mood of fighting fades from Zach's mind, he sees the many families he has destroyed.

Therefore, he vowed to continue to persevere in the good deeds of his parents. He helped rebuild the house he had destroyed, and when the repairs were completed, he disappeared into Zaun's vast network of pipes.

Now Zach lives alone, inhabiting the pipes and caves scattered throughout the city, bathing in the various emotions of the city's residents.

Sometimes he feels colorful, but other times he feels sad because he absorbs both the good and the bad of the city at the same time.

He gradually became an urban legend in the legends of the Zaun people, a mysterious creature that would occasionally emerge from crevices in the rock or through pipes.

Most of the time he appears to help those who are helpless, but when trouble arises, when the mood of the city becomes dark and bitter, his presence may make some people shudder.