The Iron Age Celtic tribes of Europe were, even at their zenith, a mysterious people even to their closest neighbors. Though their bards knew many centuries of oral traditions and their priests and mystics had charted the movement of the stars and seasons, they never committed most of their knowledge to writing. Most of what we know about these fascinating peoples comes from the accounts of Roman and later Christian authors who detailed the lifestyles, practices and beliefs of these peoples, albeit through a very biased set of lenses that none the less paint a fascinating portrait of a society well aware of the world around them.
Among other elements of the world in which the Celts lived, their sages and seers noted the movements of the stars in the sky. Though a truly complete picture of Celtic astrology is likely lost forever, enough of their ancient wisdom was recorded to create an interesting system of astrological correspondences rivaling those of other societies. Through observing the skies above and the planets and stars therein, the ancient Celts found a number of traits on Earth being reflected by the stars. These traits were eventually codified into the Celtic zodiac, a system based on the observations of thirteen separate constellations that these ancient peoples knew very well.
Like many other civilizations that emerged around the same time, such as the Babylonians and Chinese, the Celts saw the images of animals they knew on Earth reflected in the stars above them. Ancient Celtic seers noted thirteen major constellations in total, each of them reflecting a different animal that the Celts of early Europe knew in great detail. Some of these animals, such as the hawk and the stag, were drawn from daily observations of natural animals in their environment. Others come from a more mythological perspective, such as those of the sea serpent and the unicorn. A few involved uniquely Celtic archetypes, particular the separate constellations of the black horse and the white horse.
Based on their observations of these creatures, the Celts conceived of a wide range of astrological traits that were reflected from the constellations on to Earth. Each trait associated with these animals in Celtic folklore is found in a wide range of ordinary human beings, from the powerful personalities and protective natures of the green dragon to the affectionate, domestic attitudes of the seahorse. Though the full depths of these systems is apparently lost forever, their legacy endures.