Gastly

Gastly is a rare Ghost-type Pokémon from Kanto region. It evolves into Haunter when fed with 25 candies and its final evolution form is Gengar.

Pokédex description
Gas Pokémon

''Gastly is largely composed of gaseous matter. When exposed to a strong wind, the gaseous body quickly dwindles away. Groups of this Pokémon cluster under the eaves of houses to escape the ravages of wind.''

Evolution family
Gastly is the part of a three-member family.