Beheeyem

Beheeyem is an extraterrestrial psychic-type Pokémon species originally discovered in the deserts of Unova, next to a UFO crash site, about 50 years before its Pokédex entry was written. Its juvenile stage is known as Elgyem. Both are also known as the Cerebral Pokémon.

Biology
Elgyem and Beheeyem are medium-sized humanoids known for their disproportionately large heads and extraordinary psychic abilities. They have smooth hairless skin, luminous green eyes, distinctive marks on their foreheads, with the central mark shaped like the letter Y, and no visible mouths whatsoever. Like all Pokémon, they can consume fruits. Their legs are extremely short and toeless, and they prefer to move around by levitating, presumably by means of telekinesis. Their arms are skinny, but terminate in broad hands with three short luminous fingers, each colored differently: one red, one green, and one yellow.

They're a dioecious species, with a gender ratio of one male to one female. Like all documented Pokémon, they're oviparous. Despite being extraterrestrials, they can breed with any other Pokémon species in the Human-like egg group, and the offspring will be of the same species as the mother, as per the typical norms of Pokémon reproduction.

Wild populations of this species are currently only known to exist in Route 14 and the Celestial Tower in Unova, Mount Hokulani in Alola, and the Bridge Field in Galar.

Elgyem
Members of this species begin life as Elgyem: a 50 cm tall creature with bluish-grey skin, a mostly humanoid body plan, a large oval head, oval-shaped green eyes and a short tail. When battling an opponent, it makes use of its psychic abilities to "squeeze" its foe's brain to provoke severe headaches.

When an Elgyem stands close to a television set, it will interfere with its working and cause strange scenery to show up on the screen, which is believed to represent images of its homeworld.

Beheeyem
When Elgyem evolves into Beheeyem, it doubles in height and more than triples in weight. Its skin color changes from grey to brown, and its head broadens at the base. The shape of its head and body gives off the appearance of wearing a very large hat and a trench coat. Its eyes, unlike Elgyem's, are conjoined, and have black pupils.

Beheeyem is known for its ability to interfere with its opponents' minds and manipulate their memories. They communicate by flashing their luminescent, differently-colored fingers. They're occasionally found hovering over wheat fields, and according to the Galarian Pokédex, have been responsible for the mysterious disappearance of Dubwool whenever they visit farms.