Hollow Knight Silksong features a variety of bosses. One of them appeared thanks to a fan's idea.
In 2019, Seth said that he was fighting Ewing's sarcoma (a type of cancer) and dreamed of communicating with the developers. In the end, it was not limited to a simple conversation, Team Cherry offered him to create his own character.
He decided to name it in his honor — Seth. Soon after that, the player died, but now Hollow Knight Silksong has his character, acting as one of the bosses.