Muscle Feather is an item in the “Vitamins” category (Medicine). It costs ₽300.
In-game descriptions
| Black / White · Black 2 / White 2 · X / Y · Sun / Moon · Ultra Sun / Ultra Moon · Let’s Go, Pikachu! / Let’s Go, Eevee! | An item for use on a Pokémon. It slightly increases the base Attack stat of a single Pokémon. |
|---|---|
| Sword / Shield | An item for use on a Pokémon. It slightly increases the Attack base points of a single Pokémon. |
Where to find it
Not placed on the atlas maps (so far: Red/Blue and Generation 3).
Sources : PokeAPI (items, item_flavor_text, machines) · atlas · pokeemerald species_info.h