The name Staryu is derived from star (referring to its shape) and yu (a corruption of you). Yu is also the Chinese word for fish (魚). Its Japanese name ‘Hitodeman’ (ヒトデマン) is probably derived from an alternate reading of 海星 kaisei, meaning ‘starfish’.
Staryu is a golden starfish-like monster with five appendages. These surround an exterior organ called the core, which is held in place by a golden ring looped around Staryu's left leg, similarly to a ring mount. If any of Staryu's appendages are lost, it can grow them back with ease provided the core is still intact. The core resembles a red jewel and is similar to a madreporite.
When the sun goes down, the core usually glows its brightest. Many Staryu will float from the seafloor to the surface and align themselves with stars of the night sky as their core flickers, displaying a connection with the celestial bodies of space. If a Staryu becomes weak, its core will grow faint and flash slowly. They can be found at the very bottom of the ocean on the seafloors or in the dark, calm waters of caves. There are times, however, when Staryu finds itself in rivers.
PLEASE TAKE A LAMINATED IMAGE OF STARYU FROM INSIDE THE CACHE AND HOLD ONTO IT. REMEMBER TO KEEP A LOOK OUT FOR FURTHER CACHES IN THIS RANGE, APPEARING IN THE FUTURE. YOU GOTTA CACHE 'EM ALL!!
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AscottAmblers

Image & information sourced from Bulbapedia (www.bulbagarden.net)
This is official artwork by Ken Sugimori & the contributor (Bulbapedia) claims this to be fair use.