Alolan Growlithe is pure Water-type, while Alolan Arcanine are Water/Fire. They were bred specifically to help protect and rescue the denizens of Alola in case of a volcanic eruption. Arcanine in particular can survive the scalding hot water and to protect the people from boiling alive.

Marshadow is of the Psychic-Electric-type, and is the creature that brought forth the Sun and Moon Dials in Alola and Kalos. It is an interdimensional being, and is using the Sun and Moon Dials as a means of syphoning energy from Solgaleo and Lunala. Think of it as a parasitic worm in a sense.

The Gen 6 and 7 Starters as well as Rockruff are capable of transforming--not just Greninja. The reasoning behind these transformations have something to do with Zygarde.

The end game comes down to Perfect Zygarde versus Marshadow. Marshadow, Solgaleo, and Lunala also have special transformations for themselves.

Dragonite has his very own Z-Crystal, or Dragonitium Z. No Mega Evolution or Alola forms.

Mega Evolution is post-game only.

The type-based Z-Crystals all come from Totem Pokémon. However, core opponents like Hala or Guzma will carry the species-related Z-Crystals.

Lt. Surge, Looker, Zinnia, and all of the past League Champions are all in the game.

Postgame after the Zygarde vs. Marshadow confrontation will involve building a league out of the Trial Captains you have met on your journeys--as their work has finally come to an end. You can rematch the Kahunas at the Pokémon League on the artificial Island as the new Elite Four. The Champion, on the other hand, is somebody you will get to meet soon enough.

Additional new information to watch out for? A Fire-type legendary that causes mischief from a shrine near a body of water; the Ice/ghost-type snowman Pokémon; Solrock and Lunatone's Z-Crystals; and some of the Trial Captains on the third island.

Don't be surprised if some of this leaked information turns out to be released in the September 6th trailer. See ya!