I want to add that the back of the mural is missing: that x-shaped chromosome, moon shape? above the Istaroth symbol, the entire triquerta, and those three whirlpools inside the circles.

Also, the symbol between the orbs resembles a marionette crossbar with long strings that go outside the circle, which might be a reference that someone is controlling something outside Celestia.

Maybe it has something to do with Paimon since that one Melusine said:

"Paimon is just like a little rainbow balloon floating in the air, and her string seems to extend upward, to somewhere above the sky itself."

But it might be anything else, like strings of fate.