Shells are the physical matter that are occupied by Pearls, and they are made of an indestructible material that can be any shape or size, but can move freely and swiftly. Thus most Shells have some form of legs or wings, as they exclusively live on land. Shells were all created at one time, and cannot be altered, created or destroyed. They were all made by the God of Life, along with Fairies, who are also indestructible, and the original Pearls, who are destructible and very mortal.
The defining feature of Shells is that they are usually very large, compared to Humans, and are made of a substance that looks similar to Obsidian, and have a crystalline structure with jagged edges and sharp points. They can be found anywhere on Jove, and there are some at the bottom of Jove's seas, underground caverns and underground oceans, because they are too heavy to be lifted out.