Fragments of the rich and complex mythology of the ancient Celts of pre-Roman Europe were preserved in the monasteries of early Christian Ireland and in stories first written down in medieval Wales. The exploits of Culchulainn and Fionn mac Cumhaill and of Deirdre and Rhiannon have their roots in the Iron Age and have come down to us from the tales of Celtic bards and storytellers. The myths relate epic stories of heroic ancestors, when the divine...