Blasphemous 2

You need to find the Chime of the Twisted One at the top of the Mother of Mother's area and equip it to your chants on the prayers page of your inventory. Now you have to find all 10 diamond shaped infinity signs in the background of various rooms throughout the map and hit down and B to use the chime to unlock the symbol.

I used the following link for the locations and it was very helpful:
https://steamcommunity.com/sharedfiles/filedetails/?id=30255...

Also, this is super easy if you wait until near the end of the game after you have unlocked the ability to transport between Prie Dieus.