Australian Aboriginal mythology
This 'Rainbow Serpent', a snake of enormous size, lives in the deepest waterholes. It came from a larger being which can be seen as a dark streak in the Milky Way. It shows itself to people in this world as a rainbow as it moves through water and rain, shaping landscapes, naming and singing of places, swallowing and sometimes drowning people; strengthening the knowledgeable with rainmaking and healing powers; blighting others with sores, weakness, illness, and death.