Eternatus

Eternatus (Japanese: ムゲンダイナ Mugendaina) is a dual-type Poison/Dragon Pokémon introduced in Generation VIII.

While it is not known to evolve into or from any other Pokémon, the player battles a powered-up form of Eternatus known as Eternamax Eternatus in the climax of Pokémon Sword and Shield. This form is also briefly seen when it uses its signature move, Eternabeam, but cannot be acquired legitimately in-game.