It was about a girl who was either reborn or reincarnated in a otaku game or novel and one thing I remember is that in one chapter there were soldier who were fighting plant monster in a cave(?) and when the plant monster is destroyed they leave mana stones. Also I think the girl was about to use magic.
It was a empress manga that took time in the old time? She had black hair and in one chapter she told her maid to pretend to be her, that maid covered her face with a black hat and we find out she is pregnant.