Griseous Pearl
Griseous Pearls can be used to change Giratina from its Altered Form to its Mega Form.
How to find them
Griseous Crystals were obtainable during the 2016 Halloween Event by purchasing them for 20,000 
Halloween Sweets.
How to use it
The Griseous Pearl can be used to change Giratina into its Mega Form. This can be done by giving a Giratina the item to hold and it will change forms. If the item is removed from the Giratina, it will revert to its Altered Form.
Other
- Griseous Pearls are tradeable.