The Tuatha De Danann soon overcame the Firbolg, and drove them, after the Battle of North Moytura,[4] into the islands along the coast, to Aran, Islay, Rachlin, and the Hebrides,[5] after which they assumed the sovereignty of the island to themselves.
This sovereignty they maintained for about two hundred years, until the ancestors of the present Irish, the Scots, or Gaels, or Milesians, as they are variously called, landed and beat the Tuatha De Danann, and reigned in their stead until they, too, in their turn were conquered by the English. The Book of Conquests is largely concerned with their landing and first settlements and their battles with the De Danann people whom they ended in completely overcoming, after which the Tuatha Dé assume a very obscure position. They appear to have for the most part retired off the surface of the country into the green hills and mounds, and lived in these, often appearing amongst the Milesian population, and sometimes giving their daughters in marriage to them. From this out they are confounded with the _Sidhe_ [Shee], or spirits, now called fairies, and to this very day I have heard old men, when speaking of the fairies who inhabit ancient raths and interfere occasionally in mortal concerns either for good or evil, call them by the name of the Tuatha De Danann.
The first battle of Moytura was fought between the Tuatha De Danann and the Firbolg, who were utterly routed, but Nuada, the king of the Tuatha Dé, lost his hand in the battle. As he was thus suffering from a personal blemish, he could be no longer king, and the people accordingly decided to bestow the sovereignty on Breas [Bras],[6] whose mother was a De Danann, but whose father was a king of the Fomorians, a people who had apparently never lost sight of or wholly left Ireland since the time of their battles with the Nemedians over two hundred years before. The mother of Breas, Eiriu,[7] was a person of authority, and her son was elected to the sovereignty on the understanding that if his reign was found unsatisfactory he should resign. He gave seven pledges of his intention of doing so. At this time the Fomorians again smote Ireland heavily with their imposts and taxes, as they had done before when the Nemedians inhabited it. The unfortunate De Dannan people were reduced to a state of misery. Ogma[8] was obliged to carry wood, and the Dagda himself to build raths for their masters, and they were so far reduced as to be weak with hunger.