Dusk Stone is an item in the “Evolution” category (Items). It costs ₽3000.
In-game descriptions
| Diamond / Pearl · Platinum · HeartGold / SoulSilver · Black / White · Black 2 / White 2 | A peculiar stone that makes certain species of Pokémon evolve. It is as dark as dark can be. |
|---|---|
| X / Y · Sun / Moon · Ultra Sun / Ultra Moon · Let’s Go, Pikachu! / Let’s Go, Eevee! · Sword / Shield | A peculiar stone that can make certain species of Pokémon evolve. It holds shadows as dark as can be. |
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