Deoxys

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

Trivia

 * On September 20, 2018, Mewtwo was replaced with Deoxys' Normal Forme in EX Raid Battles.
 * Contrary to other Mythical Pokémon, Deoxys will be able to be transferred to Professor Willow.