A Mysterious Core. It's impossible to see what is inside.
You can use this item to create one (1) Pacapillar (Common). Use this item along with Psidium Berry to make a Rare Pacapillar. For a Super Rare Pacapillar, you'll need to use BOTH a Psidium AND Fragaria Berry. For Natural Subspecies, use a Dubious berry on an SR slot, and for Unnatural Subsecies use a Forbidden Berry on an SR Slot.
Using an Olera Berry along with this item will not upgrade the overall rarity of your Pacapillar, but it will grant you one mutation.