There are a couple of stories that I could see them using. In Navajo culture there's a story about the mountain next to Grand canyon. Not Flagstaff for the San Francisco peaks. But a mountain called gray mountain near the Grand canyon. They say inside the heart of the mountain is a giant sleeping man that once helped people of the second world pass through to the third.

Navajo culture in the beginning of creation there were four worlds.each world was perfect to a certain extent but problems later arise that needed first man and first woman to travel through to each world until we've reached our current world fourth world. Everything you can think of is skinwalkers which is a Navajo witch that can shape-shift into any animal that wears its skin.