Anistar City and the Pink monument's secret!

So I wanted to bring up Anistar City as a topic for discussion, but specifically not on the city itself but the Giant Pink Rock/Statue/Monument thing that stands in the city. So we know this Pink Monument has something to do with Mega stones, it was used to help us discover mega stones in Kalos too. Maybe have said it relates to Diancie due to the color and design of the rock. But now something has come up that may change our perspective of what this Rock's true purpose is, and it's secrets.

I would like to point to this Poster for the new Mega Act coming out soon.

Spoiler

Notice anything interesting? That's right in the center of the poster we see the giant Pink Monument. Now we could just debunk any theories and just say this is there only cause Ash makes it to Anistar city but i mean. If you are going to put this thing in the Poster of a special and have the new Zygarde perfect form towering over it, I guarantee it plays a specific role of some sort that may relate to Zygarde as well. What are your guys theories on the giant Pink Monument? Do you think it holds the true secret to mega evolution? Where did it come from exactly? Whats the gold piece on it for? Does it have any relation to Zygarde?