Danu is the mother of the Irish "gods" [in Buddhist terms, terrestrial and extraterrestrial devas], linked to the goddess Dôn in Wales. Her tribe is the Tuatha Dé Danann, the People of the Goddess Danu or Ana.
Invading Ireland on the first of May, the Tuatha Dé Danann battled the Fir Bolg, and eventually won an uneasy peace. In their turn the Tuatha Dé Danann were displaced by the mortal Milesians and retreated to the sídhe, or hollow hills, to become the Faery Folk of legend.
The coming of the Milesians is likely a mythologizing of the Christian conversion of the Isle that ousted the pagan gods and goddesses. Danu is a goddess of fertility and plenty, and there is evidence that the river Danube is named for her. As mother of the faeries she is close to the land and waters. More