Muscle Feather flings for 20 power, a Vitamins item since Generation V
PokéAPI item 607 of 2,223, Vitamins category, Medicine pocket
Effect, in PokéAPI's words
Muscle Feather: “Increases Attack effort by 1.”
Used on a party Pokémon: Increases the target’s Attack effort by 1.
Games
Muscle Feather is listed in the text of 7 version groups, first in Generation V
Game index by generation
IIIIIIIVVVIVIIVIIIIX
Named in
Black and WhiteBlack 2 and White 2X and YSun and MoonUltra Sun and Ultra MoonLet's Go Pikachu and Let's Go EeveeSword and Shield