Gastly

A being that exists as a thin gas. It can topple an Indian elephant by enveloping the prey in two seconds.

Little Grudge: During your opponent's next turn, if this Pokémon is Knocked Out by damage from an attack, discard an Energy attached to the Attacking Pokémon.

Nightmare (20): Flip a coin. If heads, your opponent's Active Pokémon is now Asleep.