Central to the plotline of Pokemon Ultra Sun and Ultra Moon is the mysterious Pokemon Necrozma, which apparently came to the Pokemon world from another dimension. Dusk Mane Necrozma's Attack stat will be higher than Solgaleo's while Dawn Wings Necrozma's Special Attack will be higher than Lunala's.
Solgaleo and Lunala will receive the exclusive Z-Moves Searing Sunraze Smash and Menacing Moonraze Maelstrom, respectively. Additionally, each form will have its own new Z-Move.
This form of Necrozma manifests when the Pokemon takes control of both the body and mind of the Legendary Pokemon Solgaleo (Sun), absorbing the light energy that pours out of it. This Necrozma form shoots energy that glows darkly from the black parts of its wings.
The trailer also reveals that Necrozma will have access to a new move called Photon Geyser, although its effects are now unknown. Hopefully, it won't get in the way of Pokemon Ultra Sun and Ultra Moon telling a coherent, engaging story that actually has a satisfying ending.
A Ghost-type Z-Move, Menacing Moonraze Maelstrom can be used by a Lunala that knows Moongeist Beam and is holding Lunalium Z. Similarly to Searing Sunraze Smash, Necrozma can use this Z-Move if it knows Moongeist Beam and is holding Lunaliam Z, and it also ignores the enemy Pokémon's Ability.
In the game, the more Pokemon Ultra Sun and Moon players communicate with Rotom Dex, the more helpful it will become to the player.
It definitely seems like Roto Loto is filling a similar niche to the Player Search System from Generation VI, letting you change up encounter rates, boost EXP gained and more. Points earned from battle, but most interestingly it unlocks a new Z-Power for the Rotom Dex itself when maxed out which lets you use not one, but two Z-Moves per battle. Rotom may also allow the player to use a Z-Move a few times per battle. Both titles will require approximately 3.6GB of space.