Cloyster is a black bivalve mollusk Pokémon. It resides within a light-gray shell, enveloped by a second jagged, blue-violet outer casing. This Pokémon has one spike resembling a barb above its head and several conical horns on its outer shell. The shell's hardness surpasses that of a diamond, with spikes even tougher; the intensity of tidal currents influences the size and sharpness of these spikes. Its pearl-like face features two white eyes and a mouth. Apart from its face and head, Cloyster’s internal anatomy remains unseen. Once it closes its shell, it cannot be opened from the outside. This formidable defense enables it to endure bomb blasts or missile strikes.
Cloyster typically opens its shell only to attack. However, it can retaliate effectively with its shell tightly shut. It launches its spikes rapidly at enemies, keeping them at bay. In Generation I, Clamp was its signature move. The same system used for launching spikes also propels it through water. By swallowing seawater and ejecting it towards the rear, it uses siphon-jet propulsion to swim. Evolving from Shellder via an Evolution stone, Cloyster is seldom found in the wild but may be discovered on the sea floor among rocks and coral. Interestingly, it hunts Slowpoke tails on land. Cloyster and Shellder are related to Gastrodon, while Kingler is a natural predator of Cloyster.
Evolution
Cloyster evolves from Shellder.
(Source: Bulbapedia)
