It is on a post-apocalitpic setting, much of mankind has been wiped out, there´s few technology left, there is a wall dividing the world built by the people of the past. the reason of why everything is like that is like a mystery that gets solved as the story goes.

Now, there is a cult of people who worship the wall as it contains the long forgotten technology of the past. This cult kidnaps people to sacrifice them in the wall, this structure has a wrathfull ai that hates mankind (like AM from I have no mouth and I must scream), the main character gets trapped inside it and there he meets a woman who ends up dying, as her last words, she tasks the main character to find her lost sister and take care of her. The main dude manages to escape the wall and his main goals are fullfiling the will of the girl and taking revenge on the cult.

I want the arc of the guy to revolve arround his survivor´s guilt, how he struggles to bond with people as he fears losing friends again.