I Became a Level -99 Vicious Lord - Chapter 74:

Schiller became Batman’s teacher, a professor of psychology at Gotham University.On the first day, Bruce Wayne entered the psychiatric clinic.Schiller had to open the Meiman chat system and posted the first post: Batman asked me the meaning of life, how should I answer? It’s a hurry to wait online.Thanos: It is recommended to kill directly.Professor X: Don’t listen to the upstairs, I’ll use your mind-reading skills…Schiller Andel Rodriguez, a world-class master of criminal psychology, the most famous psychology professor at Gotham University, his students are both superheroes and super criminals, but he does not belong to any of them, Batman likes to call him “Professor”, Joker calls him “the coolest lunatic”, Scarecrow calls him “Arkham slipper”, and Nick Fury thinks he’s a “getter.”Be Batman’s teacher, Spider’s godfather, Iron Man’s psychiatrist, Schiller’s journey to American comics, starting with Batman at the beginning.[Other than translator’s site, all other sites have google translated content, beware. Don’t comment bad translation after reading other site content.]

Grounded in the Transcendent, framed by the Sequence, the Wizard ignited the Source Energy and spewed out a mist of Origin Energy.The roaring sound of steam echoed through the entire epoch!In the depths of shadow and the dark tide.Countless greedy, twisted, polluted, and deformed gazes were coveting this roaring new World.The World began to buzz with activity!A certain Wizard, however, was lurking silently in a corner.“I like to develop!”“Then, what is the deal with those Demon King's heads and Evil God's skeletons?”“I told you, I like to develop, and this is the fate of those who hindered my growth!!”

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