kind of post apocalyptic world. Basically suddenly donguons with mosters appear in a modern world and some people gain supernatural abilities. Usually has a game like feel to It. For example people with abilities are called players and they can level up. Some examples: Solo Lveling, SSS class suicide hunter, Leveling withthe gods.
Novels is a historical setting (usually European) – Getting transmigrated into a novel the main character read before, often as a villain.
Unlimited flow novels (horror)- MC is forced into completing scenarios or levels.