Stellar Echo: Heart of the Myst - Chapter 37 - : Arcane Library

Ming Liuyi transmigrated into a novel she had read, and to make matters worse, she was placed into the body of the novel’s antagonist who shares the same name. The original Ming Liuyi, bullied into marrying a cripple, decided to abuse the rich male lead, Yao Zizhou, until he went into a vegetative state. Ming Liuyi knew she had three months of safety before Yao Zizhou woke up and took his revenge. But for some reason, she was drawn to him, and when she touched him, her spiritual energy began to stir.

No one suspected that Yao Zizhou would actually still be perfectly aware of his surroundings, though he couldn’t move. He continued his days in great confusion when his arranged wife from hell was suddenly replaced with a sweet, nice girl, who actually cared for him dutifully and spoke to him with gentle words. It aroused his curiosity, but right before he could wake and see her, she fled. Yao Zizhou huffed in annoyance. There was no way he would let her escape his clutches.

In this world, orphans or just anyone without any hope for this world can apply to become a “walking target”. Their sole purpose is to be a practicing dummy for the students of the sect who train to become “Demon Hunters”. These students need “walking targets” to test their training on living, walking beings of flesh and blood.
In exchange, they will be provided with food & shelter.
Their existence value is lower than a slave, but if they manage to survive a few years they can receive a life long pension.

Xiao Han is such a “walking target”. One time he witnessed a powerful Demon Hunter disposing a demon. When the demon died, a fragment of the demon that managed to escape entered Xiao Han’s heart. No one saw that, and even Xiao Han himself only felt some discomfort for an instant.

But that thing in his heart soon gave Xiao Han visions, and the first one is of a cultivation method which allows Xiao Han to absorb damage to enhance his body. A perfect cultivation method for a “walking target”.

- Description from Novelupdates

In novels with a stud there is always a Senior Martial Brother like this:

In the early stages of the novel, his innate talent is high, his cultivation is good, his appearance is handsome, and he has an intelligent, cute younger Martial Sister as a fiancée.

In the middle stages of the novel, he is caught unprepared and defeated by a young disciple (the protagonist) in the sect who’s hardly remarkable at all. From then on, he falls from his godly altar and loses his brilliance. Even his young Martial Sister leaves him for someone else.

In the late stages of the novel, he continues to turn dark, going down the Demonic Path and becoming the major villainous boss. However, the protagonist still ruthlessly defeats him and his soul is eternally sealed.

Once Qin Mo opened his eyes, he discovered that he had become this Senior Martial Brother.

- Description from Novelupdates