Gastly

Gastly is a Ghost/Poison-type Pokémon introduced during the first generation Pokémon games. It evolves into Haunter at level 25, which evolves into Gengar when traded. Gastly are mostly composed of poisonous gas, which surrounds what appears to be their main body.

Gastly appears in Super Smash Bros. for Nintendo 3DS as a Smash Run enemy. As it is engulfed in poison gas, it is immune to melee attacks and can only be taken out with projectiles. It can damage players on contact and will sometimes follow them.