I recommend the book "Online Games: Defying Monsters" to you. The protagonist inexplicably became a monster that gave players experience and money. Later on, he became the Skeleton King that shocked the game. Then, he brought a group of underlings to the Otherworld. The word count of this book is between 300,000 to 1,000,000. It meets your requirements. I hope you like this fairy's recommendation. Muah ~😗