Gastly

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

Trivia

 * During the Halloween event in 2017, there were shiny forms of Gastly family members added to game data, although they weren't released to be caught in gameplay.
 * Shiny sprite of Gastly was updated on November, 2018 after several complaints from the community.