These are notes I have made that might link this game to Evil dragon.
Spoilers for Awakening and Echoes Endgame.
This is what I gathered so far. (not too much)
Evil man with white hair (magic one) might be Forneus maybe. Or better yet, Byleth with that "hidden power?"
Here is something interesting I noticed:
The symbol looks "somewhat" similar but what strikes me is that the evil man symbol has 6 lines around a center point like the Grimleal symbol possibly hinting that this is grima with his eyes closed (to show he is not born).
Maybe this "religion" are working for old man/Byleth to begin the creation of Grima maybe to gather dragon blood. (this is not explained)
I had a horrible idea that probably won't happen but what if Sothis is killed for dragon blood?
Really this is just me coming up with a theory for this symbol that we know nothing about.
Also the Valentian Endgame wasn't long ago so maybe they planned to have this connected?
P.S.
Probably just a coincidence but just wanted to point out some "links" . Had some other points but felt like they weren't worth talking about. Just something while I desperately wait for release.