FawnSadb, daughter of Bodb the Red, and the deer woman who loved Fionn. She is a Moon Goddess who presides over fertility.  Sadb was turned into a fawn by the Dark Druid.  Escaping his spell for a while, she became the mistress of Fionn, bearing him a son. 

In Irish mythology Finn mac Cumhail, the legendary leader of Ireland's heroic band of warriors known as the Fianna, cornered a beautiful white deer, which his hounds then refused to dispatch. That night Finn was visited by the goddess Sadb, who explained that a spell had turned her into the deer Finn had chased, a spell from which his love could release her. Though they became lovers, the magician who cast the spell reclaimed Sadb when Finn was away repelling a Viking raid on Dublin, and though the Fianna searched the land, Sadb could not be found. Some years later however, another of Finn mac Cumhail's hunting sorties tracked down a naked, long haired boy whom once again his hounds refused to kill. The boy did not know his father but knew his mother to be a gentle hind who lived in fear of another man. Details of the story convinced Finn that this was his son, and he named him Oisin, meaning fawn. Oisin too became a heroic Fenian warrior, though he also inherited some of his mother's gentler arts and was acknowledged as Ireland's greatest poet.