A Grirua's body is made of a constantly flowing and shifting ooze. Grirua can construct and color their ooze to form false images around them, splattering anyone who tries to attack them with poison before fleeing.
To protect themselves from danger, they hide their true identities by transforming into people and Pokémon. Born from polluted sludge in the sea, Grirua's favorite food is anything filthy.