Calorians are a species of primitive humans native to Calor, a planet in the solar system closest to Earth. Not much is known about them, but they do seem to practice a primitive religion in which they pray to a tree, and worship a being called "Ka-Ma".
One of Hal Jordan's earliest missions as Green Lantern was to rescue the species from an entity known only as Dryg that was terrorizing them.
- Green Lantern 1 (Vol. 2)