https://www.polygon.com/2017/10/17/16488462/pokemon-ultra-sun-and-ultra-moons-story-trailer-is-dramatic-as-hell

We already know that Pokémon Ultra Sun and Pokémon Ultra Moon, the series’ upcoming pair of Nintendo 3DS games, plunges the series into darkness. A very, very intense story trailer released this week puts a much finer point on just how dark things will get, however.

The tagline is “This isn’t the Alola you thought you knew,” and that may be an understatement. Ultra Sun and Ultra Moon return players to the tropical region, which has since been robbed of all of its light. The mysterious legendary monster Necrozma has something to do with it, as do the even stranger Ultra Beasts. It’s up to Pokémon trainers — and some familiar faces from last year’s Pokémon Sun and Moon, like Lillie and Island Master Hala — to help restore the region to its former state.