In Pokémon Legends: Arceus, when the Griseous Core is used from the satchel on Giratina, it switches between its Altered and Origin Formes.
In Pokémon Scarlet and Violet, if a Giratina is holding a Griseous Core, it changes to its Origin Forme. Additionally, it boosts Giratina's Dragon- and Ghost-type moves by 20%.
||When used on Giratina, this large, glowing gem wells with power and allows the Pokémon to change form.
||An item to be held by Giratina. This large, glowing gem wells with power and allows the Pokémon to change form.