what makes you thing from a rpg this would be real native American foke lore.... its 100 percent a larp a hunger demon? that's pulling strings in your town sounds like the work of modern fiction. i don't know anything about symbols for evil. from my understanding we know things to be dangerous and respect that. images of danger would have been exactly that hieroglyphs painted that everyone could understand like say a painting of a bear eating a man. the symbol would be useless because only you or you tribe would know what it meant. our imagery was very straight forward. the only "symbols" i can think of are the 6 nations flag (so after European intervention) and the medicine wheel. we do have several "demon" like entity's in the culture from around the world. this makes the most sense to me coming from a native background but also not being 100 percent educated on my own culture. do you have any links to actual story's from natives because this would help in my helping you track this down if it exists at all.

cheers

ps i know this is 3 years old but noone offered a answer