- Voice actor: Ed Paul (both English and Japanese)
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. Its height is 4'03" and weight is 0.2 lbs.
Due to having a body made of gas, Gastly can slip into any place it wants. However, Gastly's body will dwindle away when exposed to a strong wind but it can probably regenerate itself later. A Gastly is capable of toppling an Indian Elephant within two seconds by enveloping it in poisonous gas.
Despite Gastly's evolutionary level, it is quite powerful at using special attacks such as Shadow Ball, Dark Pulse, Thunderbolt, and Energy Ball. Gastly can learn quite a few moves with all sorts of disruptive effects such as Will-O-Wisp, Confuse Ray, Hypnosis, Taunt, and Embargo.
There have been claims that on rare occasions, a Gastly can gain the ability to speak like a human and transform itself. However, it apparently can communicate with telepathy.
Gastly can learn and use the elemental punches, despite appearing to have no hands. It can, however, create hands from its gas.
As a Ghost Pokémon, Gastly tend to be pranksters that go scaring people just for the fun of it. They are also proficient at sneaking up on unsuspecting prey and putting it to sleep or poisoning it through their skin. As Gastly's body is blown away by wind, groups of them gather under the eaves of houses to prevent being blown away.
- Main article: Pokémon food
As the victims of Gastly's gas enveloping technique have been called prey, it can be presumed that it derives energy from them. It may also lick its prey.
Gastly first appeared in The Ghost of Maiden's Peak. This Gastly had the ability to talk and shape-shift. He kept posing himself as the spirit of the woman which legend said turned to stone after many years of waiting for her love to return to her. As the ghost of the maiden, Gastly kept on toying with the minds of young men.
The first time a regular Gastly appeared was in The Tower of Terror. Sonic, Ash and friends went to Lavender Town in search of a Ghost Pokémon to aid Ash in defeating Sabrina. It reappeared in a flashback in the following episode.
A pair of Gastly were among a group of Ghost Pokémon living in an abandoned mine in Fear Factor Phony. The Ghost Pokémon couldn't stand the partying Psychic Pokémon that lived in the nearby town, so they created a Haunter-like illusion to scare everyone away.
A Gastly appeared in For Ho-Oh the Bells Toll!.
A Gastly made a brief cameo appearance in Giratina and the Sky Warrior.
A Gastly appeared in Ghoul Daze!.
Gastly, Gas Pokémon. It is usually invisible. Its specialty is Hypnosis. Although it can sneak in anywhere with its gaseous body, it can also be blown away by wind. Because of it's gaseous body, some researchers believe this Pokémon is a multidimensional being.