Prism Scale is an item in the “Evolution” category (Items). It costs ₽2000.
In-game descriptions
| Black / White · Black 2 / White 2 | A mysterious scale that evolves certain Pokémon. It shines in rainbow colors. |
|---|---|
| X / Y · Sun / Moon · Ultra Sun / Ultra Moon · Let’s Go, Pikachu! / Let’s Go, Eevee! · Sword / Shield | A mysterious scale that causes a certain Pokémon to evolve. It shines in rainbow colors. |
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