Cosmoem is a Pokémon in the shape of a translucent, dark-blue orb with a starscape pattern set in a golden shell-like structure. The main portion of the shell is a flat oval around the center of the orb. Eight more flat, half-oval projections surround the orb in an asterisk-shape. At the center of the main body is a much smaller black core. The upper half of the core has a thin blue line on the front, back, and each side, while the lower has pink lines. On the front are two orange semicircles, which appear to be closed eyes. The overall shape of this Pokémon also resembles an eye. When evolving, the Pokémon glows either an orange or a purple color, correlating to Solgaleo and Lunala respectively, gaining traits of either a stylized sun or a stylized moon.
Encased in its sturdy, cocoon-like shell, Cosmoem is unable to move. In Pokémon Refresh, it cannot even eat. It grows as it absorbs starlight and the dust in the air. Its body is warm to the touch. Cosmoem's shell is said to be harder than any known material. In ancient times, it was worshipped as the "cocoon of the stars" by the people of Alola.
Appearances
Main Games
In the introduction, Lillie escapes the Aether Foundation with Cosmog, nicknamed Nebby, in her bag. After Lusamine uses it to open holes to Ultra Space, Nebby evolves into Cosmoem and becomes dormant. The next part of the plot is taking Nebby to the Altar of the Sunne/Moone to save it and rescue Lusamine. Cosmoem would later evolve into Solgaleo/Lunala, where it eventually officially joins the player. In Pokémon Ultra Sun and Ultra Moon, Nebby played the same and this time, merged with Necrozma to become Dusk Mane/Dawn Wings (and Ultra) Necrozma.
Pokémon spin-offs
In the anime
Cosmoem debuted in Faba's Revenge!, where Nebby evolved. Nebby later evolved into a Solgaleo in Revealing the Stuff of Legend! after being blessed by the Guardian deities.
In Pokémon Evolutions, a Cosmoem nicknamed Nebby was used by Lusamine to open an Ultra Wormhole. It later evolved into Lunala at the Altar of the Moone and later battled and absorbed by Necrozma to become Dawn Wings Necrozma.
Origin
Cosmoem has characteristics of both a stylized sun and a stylized moon, having rays and a pair of crescents, respectively. Its enormous weight despite its extremely small size shares similarities with super-compressed astronomical bodies such as black holes and neutron stars. Given its description, it seems to be an embodiment of star formation in general. It may also be based on the idea of the world egg. When viewed from the front, its shape resembles an eye.
