Cofagrigus is a blue and yellow sarcophagus-like Pokémon with red, menacing eyes and four ebony hands that appear to be shadows. A simply designed face, which is the mask Yamask carries, is prominent on the "forehead" of the Pokémon. Its real face is covered up by parts that slide open when it is active. White, sharp fangs create a taunting smile, and flamboyant patterns veil the coffin. The coffin is said to be made of solid gold.
Ancient legends once told Cofagrigus could seal nearby humans in their bodies and turn them into mummies; grave robbers who mistake them for normal coffins get this fate. Cofagrigus is said to have once been human but having forgotten its memories from when it was alive. They also enjoy eating gold nuggets. It lives in tombs and ruins waiting for victims. Cofagrigus has been used as a symbol for the wealth of kings from a bygone era.
In a fantasy sequence depicted in Raid Battle in The Ruins!, Cofagrigus is shown to be able to open its body like a sarcophagus.
