The Hidden Grottos, known as Hidden Hollows in Japan, are various small areas dotted around the Unova region. These areas are small gaps between two trees and can be accessed by interacting with the tree. While they seem relatively empty, they have numerous features which make them very prominent; The can give out Pokémon with Hidden Abilities, usually Pokémon from within that area. In addition to that, you may find a standard item sitting in the middle or an item hidden for access with the Dowsing Mchn.
Typically, when you go to an area, once you've mined it for its interactable Pokémon and items, it is useless, the Hidden Grotto is different. The contents of the Hidden Grottos change and get regenerated repeatedly.Whenever you take 256 steps in the game, there is a 5% chance that each of the Hidden Grottos will be regenerated. When it's regenerated, there's a 40% chance of an item, a 40% chance of a hidden item and a 20% chance of a Pokémon. The chance that it regenerates can be increased using a Pass Power.
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