Mysterious Shell

Mysterious Shells appear in The Minish Cap. They serve only one purpose, namely buying figurines from the Figurine Shop, which is found in Hyrule Town. They are found all over Hyrule, in things like Treasure Chests, bushes, and even rocks. A little later on into the game, Stockwell will begin selling Mysterious Shells at 30 Shells for 300 Rupees. Link can only hold 999 at a time.

Using Green Picolyte will increase Link's chance of finding Mysterious Shells.

After Link has collected all of the figurines possible, the Mysterious Shells slot in his status screen will change into the Carlov Medal, signifying this.