"For the Celts, Religion was inseparable from the world about them, and just about every feature of the landscape was imbued with some sacred significance. Bogs were evil. Fires caused by lightning were sacred. There was not a mountain, tree, river or spring that did not have its own spirit. The unknown lurked at every step. Amid these numious surroundings it was unwise to tread carelessly, for fear of offending the gods. Even the conquering Roman legionaries were careful to make offerings to the unfamiliar deities of rivers, groves and forests that they encountered as they advanced through Gaul and Britain."

--Heroes of the Dawn:Celtic Myth