Gastly

Gastly (Japanese: ゴース Ghos) is a dual-type Ghost/Poison Pokémon introduced in Generation I. It appears as a black, spherical entity surrounded by a purple haze, with large white eyes and small fangs. Gastly's body is 95% poisonous gas, with the remaining 5% believed to be the souls of those who died from the gas. It can float, phase through solid objects, and uses its poisonous gas to incapacitate or faint its opponents. Despite its spooky appearance, Gastly is often depicted as a mischievous prankster, dwelling in old, dilapidated buildings or cemeteries. It evolves into Haunter, which then evolves into Gengar when traded or when exposed to a Linking Cord. Gastly is a popular Pokémon among trainers for its unique Ghost-type abilities and poisonous attacks.