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Piggy Bank
Piggy bank's effect takes place after leaving the shop. For example, if you leave the shop with 100 materials, you will start the wave with 120.
Item
Piggy Bank is an in-game item that can be bought from a Shop or can be found in a Crate. Most Items modify the Stats of the player, and some of them provide additional effects.
Unique
Piggy Bank is a unique item. Only 1 of each unique item can be equipped, and it will then no longer be offered in the Shop, and no longer drop from loot crates.