Gastly (Japanese: ゴース Ghos) is a dual-type Ghost/Poison Pokémon introduced in Generation I. It evolves into Haunter starting at level 25, which evolves into Gengar when traded.
Haunter (Japanese: ゴースト Ghost) is a dual-type Ghost/Poison Pokémon introduced in Generation I. It evolves from Gastly starting at level 25 and evolves into Gengar when traded.
Gengar (Japanese: ゲンガー Gangar) is a dual-type Ghost/Poison Pokémon introduced in Generation I. It evolves from Haunter when traded. It is the final form of Gastly. Gengar has two other forms.