Probably a korean novel. A novel where there are demons as enemies, and "heroes / guardians" as allies. It's a VR game in which time goes a lot faster. Main character is player who wrote the book on many raids, is #1 in the world, but yet never reached the end of the game. Also, death is final in the game, you have to restart if you died. There a 3 month event where players can start as a "normal character" instead of a hero character, and is insanely hard. MC waits till the deadline then does it, and shortly after kills 5 swamp witches to gain ton of points.