Question: is necrozma an ultra beast?
Answer: It's not an Ultra Beast, though: It's the Legendary Pokémon Necrozma, and you can find him at the Farthest Hollow on Ten Carat Hill. Necrozma is level 75, a Psychic-type, and needs to be caught with regular PokéBalls (e.g. Great Balls, Ultra Balls, or Master Balls).