Oh, I noticed two more things.
Someone mentioned the ancient crown was looking like N's crown
Thanks for noticing!
Also, I have a different theory than that Kyurem is the King (wait, King and Kyurem start with the same letter). It's that Kyurem was the husk (yes, it starts with an already posted theory) of the original dragon, and that the force of splitting caused it to soar into space, (and it found shelter inside of a meteor) then fell back to earth. The shockwave forced waves upon the Abyssal Castle, which then was completely submerged.
Do you think that the Musketeer trio could be involved somehow with the Abyssal Ruins?
The third paragraph in the texts seem to say that eating Pokémon is okay, just like the Sinnoh myths say, but the two regions are incredibly far apart! And Johto and Kanto don't justify eating Pokémon, so Unova and Sinnoh must have communicated sometime in the distant past. Speaking of which, where did N go? Didn't they say that he went to a distant region? Perhaps the region that they communicated with a long time ago.
I know this isn't the place, but you can't find the God Stone anywhere, and maybe Arceus is summoned from it. Or to bring us back to place, Kyurem, the original Dragon/King/God.
Also, today when I was playing with my Pokémon toys (yes, I still play with Pokémon toys), I noticed that Moltres and Reshiram are Fire, Zapdos and Zekrom are Electric, and Articuno and Kyurem are Ice. This is probably just a tribute to the original games, or it could have some deep Unova/Kanto connection.