you keep hearing people calling him Eternatus, it's basically a kind of Giratina Space form. "it's a brand new world" , Cyrus plan to reset the world was only stopped in the non-mega universe, could succed in the mega-verse.
do you remember the rug on the mc room? has been shown. and do remember the pattern under arceus when it appears in the game? zacian.
remember dialga being zyan with blades on it body? palkia magenta with shields on it?

decided to drop all of this info right now, just because