Since the Celts were an agrarian people, animals were central to Celtic life. Thus, animals such as the wild boar, deer, wolf, and raven figured prominently in Celtic mythology and folklore.
For example, the raven was said to be a symbol for Morrigan, the goddess of war. It was believed that she often frequented the fields of battle disguised in the form of a raven. In Celtic lore, the raven was a symbol of death and destruction; it was considered a bad omen to see a flock of ravens fly across the sky on the eve of a battle.
In the aftermath of battle, however, ravens or carrion birds were a familiar sight to warriors; indeed, the Celts were a war-like people. They also practiced what was called ornithomancy, where ravens were used by priests to divine the future. So, the raven figured prominently in Celtic folklore and mythology because it was central to the warrior culture of the Celts.
Another animal that figured prominently in this war-like culture was the boar, a symbol of physical strength, courage, and prowess in battle. In fact, boar meat was preferred by Celtic warriors during celebratory feasts. The symbol of the boar was engraved onto helmets, vests, shields, and swords. In all, the boar was the Celtic emblem of warfare. It was also connected to legends of the Otherworld or Spiritworld, where it was associated with Druid worship. According to Druid beliefs, humans could connect with animals (like the boar) in the Spiritworld through the medium of their dreams and their unconscious.
Within that unconscious realm, Druids also believed that they could connect with the salmon, the repository of wisdom. As the oldest animal in the Celtic tradition, salmons were said to be central to the pursuit of knowledge.
Meanwhile, the wolf was another revered creature in Celtic lore. Known for its resilience, the wolf was said to rule over the winter months. It presided in ceremonies from Samhain (Halloween) to Imbolc (the festival of Saint Brigid and of purification). The Celts knew February as Faoilleach, the month of the wolf, and February was a time of rebirth, purification, and renewal. Interestingly, the goddess Morrigan was said to have taken the form of the red-furred wolf when she pursued Cu-Chulainn, the legendary Celtic hero.