Shellder

Shellder is a Water-type Pokémon.

It evolves into Cloyster when exposed to a Water Stone.

Biology
Shellder is a black pearl-like Pokémon encased within a spiky, blue-violet bivalve shell. It has two round white eyes with tiny black pupils. Its enormously long red tongue is used to burrow itself into the sand to sleep overnight and also to lure and capture prey. The tongue protrudes even when its shell is closed and tugging it will cause the shell to pop open. Its soft and tender body is well-protected by its extremely durable shell, which is purported to be harder than diamonds and has historically been used by people to make shields. It can make pearls from accumulated sand, though it discards them as they are typically in its way.

Shellder has an unusually strong appetite for the tail of a Slowpoke and can develop a symbiotic relationship with the Dopey Pokémon. After attaching itself to the Slowpoke's tail, the two undergo a metamorphosis and evolve into Slowbro together. Alternatively, if it attaches to the head of a Slowpoke in possession of a King's Rock, the two will instead evolve into Slowking. These relationships allow it to travel onto land and begin a new stage in its life cycle.