The Tale of The Children of Lir
Bodb Derg was elected king of the Tuatha De Danann, much to the annoyance of King Lir. In order to appease Lir, Bodb gave one of his daughters, Aoibh, to him in marriage. Aoibh bore Lir four children: one girl, Fionnuala and three sons, Aodh and twins, Fiachra and Conn Aoibh died, and her children missed her terribly. Wanting to keep Lir happy, Bodb sent another of his daughters, Aoife, to marry Lir.
Jealous of the children's love for each other and for their father, Aoife plotted to get rid of the children. On a journey with the children to Bodb's house, she ordered her servant to kill them, but the servant refused. In anger, she tried to kill them herself, but did not have the courage. Instead, she used her magic to turn the children into swans. When Bodb heard of this, he transformed Aoife into an air demon for eternity. As swans, the children had to spend 300 years on Lough Derravaragh (a lake near their father's castle), 300 years in the Sea of Moyle, and 300 years on the waters of Irrus Domnann Erris. When the spell had ended they turned into four old frail humans and died. They were buried together in the one grave.