Deoxys

Deoxys is an unreleased Psychic-type Mythical Pokémon from the Hoenn region. It doesn't evolve into nor from any other Pokémon. It will only be available for capture when defeated as a Raid Boss during an EX Raid Battle.

Trivia

 * On September 20, 2018, Mewtwo will no longer be available from EX Raid Battles and will be replaced with Deoxys' Normal Forme.