So our 5th concubine is like only Empress and her are useful to the Emperor and all the concubines are useless 
well very soon
well very soon Spoiler!
Girl is jealous of the Empress and thinks now even Empress is not useful for ML and tries to assasinate Las. She is so dumb that she forgot that Empress can use Fire magic.
I like to post spoilers for the stories I find interesting because I don't have much time to read novel due to busy schedule you will find me in most romantic historical manhwa comment sections
thank for spoiler