For the ancient Celts, the white hart was a harbinger of doom, a living symbol that some taboo has been transgressed or a moral law broken. The white hart's reputation improved in Arthurian legends, where its appearance was a sign to Arthur and his knights that it was time to embark on a quest - it was considered the one animal that could never be caught so it came to symbolise humanity's never-ending pursuit of knowledge and the unattainable.
The white stag is a familiar creature of myth and legend. The white stag in Celtic myth is an indicator that the Otherworld is near. It appears when one is transgressing or breaking a taboo. It also appears as an impetus to quest--the white stag or hart often appears in the forests around King Arthur's court, sending the knights off on to adventure against gods and fairies.
White deer holds a place in the mythology of many cultures. The Celtic people considered them to be messengers from the otherworld. The Celts believed that the white stag would appear when one was transgressing a taboo, such as when Pwyll tresspassed into Arawn’s hunting grounds. Arthurian legend states that the creature has a perennial ability to evade capture; and that the pursuit of the animal represents mankind’s spiritual quest.