In the 3ds gravity falls game the final boss gremularth is said to be as old as Bill and he has some similar powers the townsfolk encased him in a crystal and shattered it in 4 pieces. There's a prophecy that says the one that unites the four gemulets crystal pieces will become the ultimate leader. So my theory is that the shaman who painted Bill and his prophecy on the cave wall is the same as this one. The guardians of the gemulets are some totem things. I'm not sure if it's canon but I thought I should bring it up.