As any true Pokémon fan knows, the franchise has continued to grow and evolve in so many ways throughout its 21-year history. To coincide with the release of its 20th film release, Pokémon the Movie 20: I Choose You!, the list of monsters grows by one.

Watch the latest trailer to I Choose You! above that sees Ash, Pikachu, and the whole gang in another wild adventure. A closer look and you'll see a previously unseen monster named Marshadow around the 0:30 mark. As Comic Book Resources reports, Marshadow is known as a "mythological" creature, which longtime Poké players know means its a monster so rare people consider it a myth.

The Pokémon Company has said it will soon release details on how to catch Marshadow in their recently released Pokémon: Sun and Moon games.

Pokémon the Movie 20: I Choose You! will be released in Japan on July 15. While there are no details about a U.S. release yet, we think the recent phenomenon of Pokémon Go stateside will mean a theatrical release is imminent.

Below, watch celebs reveal their secret obsessions including Pokémon, Gilmore Girls and more: