I remember there was a book where this one scientist from one world got transported into the body of someone else from another world. It was an xianxia novel. He had went into enemy territory at one point in the book and took out a little devil that had a very powerful master. He also had a mystical space, I believe.
Martial God Space, @Centennial that's the one. he gets the space first, the little devil later. he's not a scientist, though, iirc...