In Pokémon Ultra Sun & Ultra Moon , you travel to the —a post-apocalyptic Alola. Here, Guzzlord has devoured nearly everything. The few remaining humans speak of a "Prophet of the Void" who opened the Ultra Wormhole intentionally. This prophet, they claim, prayed to a Shiny Lunala (the "Blood Moon" variant) to turn all Pokémon into "Hollows" that would never feel pain again.
Empty Shells are primarily found scattered along coastal areas and specific routes in the game. pokemon dark worship empty shell