Gastly (Japanese: ゴース Ghos) is a dual-type Ghost/Poison Pokémon. It evolves into Haunter starting at level 25, which evolves into Gengar when traded.
Gastly appears to be nothing more than a black ball of ghostly matter or gas that is surrounded by a purple glow of smog. Gastly has big, white eyes and a mouth with a pair of fangs in it. Gastly's face is similar to Cloyster's, but the two Pokémon aren't related.