BlackGlasses is an item introduced in Generation II that increases the power of Dark-type moves. It can be sold for 50.
In the Johto region games, this item can be found in Dark Cave, while in the Hoenn region games, this item can be found as a hidden item on Route 116. In Pokémon FireRed and LeafGreen, one is found in the Rocket Hideout. In the Sinnoh region games, this item can be found in Celestic Town. In the Unova region, this item can be found in the Desert Resort.