The Unicorn and the Druidess, my latest book, the fourth novella in the Druidry and the Beast series, is set in Iron Age Britain during the Summer Solstice. In the ancient Celtic culture, the unicorn had a place in the turning of the seasons and the Summer Solstice festival. The Celts teamed up the White Horse with the Oak Tree to symbolize Summer and the Unicorn with Holly to stand for Winter. The vigor of the White Horse carried the Celts through Summer, while the Unicorn's endurance empowered them through the re-birth brought by Winter.
The unicorn was so important to the Celts that the Scottish adopted it as the symbol of their country. One reason is that it's the natural enemy of the lion - which represented English royals. Another reason is that it's a proud and brave beast that would rather die than be captured. In fact, in the 15th and 16th centuries in Scotland, they used golden coins called unicorns and half-unicorns with the animal depicted on them. Also, Clan Cunningham's crest features the image of a unicorn's head.
Unicorns were popular throughout Europe, including Italy. Did you know Leonardo da Vinci wrote about unicorns in his notebook? The unicorn, through its intemperance and not knowing how to control itself, for the love it bears to fair maidens forgets its ferocity and wildness; and laying aside all fear it will go up to a seated damsel and fall to sleep in her lap, and thus the hunters take it.