Resolved Main character hides his strength chapter

I'm looking for chapter where MC jumps into a hole where there are bird zombies everywhere. Looking for specific chapter where he starts hammering the labyrinth's walls and he meets an a commander lady of the enemy army.
I only have a vague memory of it, so forgive my all over the place description.

 

I think it is around 80's-90's

 

Thanks! Gonna check it out now

 

Did u find it?

 

yup thanks

 

Even i stopped at there.