Mushroom Grotto in Bloons TD 6 becomes extremely demanding in the late game on Hard difficulty, especially beyond level 100, where fortified bloons, dense MOAB waves, and high-speed rounds put immense pressure on your defense. The darkness mechanic further complicates things by limiting your effective coverage unless managed properly. To succeed, you need a well-optimized defense with strong DPS, reliable crowd control, and smart visibility management to maintain full control and survive the toughest rounds.