According to their particular characteristics different animals were used to symbolise different powers, attributes or gifts. They are often connected with the world of spirits and gods, and their sacred nature is reflected in the hunting tales of shape-changing and magic. The main Celtic animal symbols are:

purity / strength / supreme magical power / healing
One of the most ancient mythological beasts, the Unicorn is a symbol of innocence, purity, healing, joy and life. Having the form of a horse and endowed with a horn, it is also a symbol of power and virility. Thus the Unicorn is the symbol of the union between masculine vitality and virility and feminine passion and nurturing spirit. The Celts believed the unicorn taught that every action is creation, thus every day should be made to count.
Though the modern popular image of the unicorn is sometimes that of a white horse differing only in the horn, the traditional unicorn has a billy-goat beard, a lion's tail, and cloven hooves, which distinguish him from a horse. Marianna Mayer has observed in The Unicorn and the Lake, "The unicorn is the only fabulous beast that does not seem to have been conceived out of human fears. In even the earliest references he is fierce yet good, selfless yet solitary, but always mysteriously beautiful. He could be captured only by unfair means." In medieval lore, the alicorn, the spiraled horn of the unicorn, is said to be able to heal and neutralize poisons. It also aided in understanding the relationship between physical and spiritual realities. In Celtic lore, the unicorn represented a Horse sporting a horn that resembled a Flaming Spear, which was connected to the month of Tanist because the Celtic "T" was shaped like a barbed spear.
power / stamina / endurance / faithfulness / balance
A popular totem animal of the Celts, the horse was considered to be a faithful guide to the Otherworld and was associated with victory in war. The Horse was sacred to the Goddess Epona (from epos, the Gaulish word for 'horse') who was worshipped by the Gauls and was so popular that the Romans adopted her cult and built a temple to her. The horse goddess Epona was believed to accompany the soul of the dying on its final journey.

The Uffington White Horse (above), Britain's oldest and most famous hill figure, is widely believed to be a Celtic symbol representing Epona.
In Scotland, kelpies would transform themselves into horses in order to lure the traveler into their realm. Although predominantly connected with Goddess figures, the horse is also a solar creature which suggests the finding of balance between the male and female. Even today, the White Horse is regarded as sacred and protected by gleaming brasses which ward off the "evil eye."