Twin king with the oak, holly rules the light half of the year.
During the middle ages and the Renaissance, the Holly King became Jack-in-the-Green, or the Green Man. But before, in druid era, holly stood for immortality, because of its evergreen leaves.
And during the winter it was considered wise to take some holly inside your house: it would provide a shelter for those poor hungry, cold and homeless fairies and elves no one cares for.
But beware: if you left even a single leaf of holly inside your home after the festival of Imbolc, it meant certain misfortune.
Druid charity obviously had its limits.

Danu (of Dana of Anu) is the Irish mother goddess. She is associated with the creation of the cosmos, with the seasons, with life-giving rain and fertility.
Her children were the Tuatha Dé Danann, the Tribe of Danu. They ruled Ireland till they were conquered by the Milesians, the ancestors of the Gaels. From then on, the Tuatha Dé Danann literally went underground, and became the fairy folk from legend.

The holly animal is the unicorn, a mythic animal with the body of a white horse and the legs of an antelope. Its single horn resembles a spear, which is another holly symbol.
Unicorns represent magic and strength. They also symbolize purity, for they can only be tamed by someone who is still a virgin.
So if you meet a unicorn, don't let anyone see you caress it.

The Ogham sign attributed to this month is Tinne.