Encased in its sturdy, cocoon-like shell, Cosmoem is unable to move. 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, Cosmoem is one of the shortest Pokémon in existence. Despite this, it is also the heaviest Pokémon in existence, being tied with Celesteela.