Not much is known of the Tuatha de Danaan prior to their invasion of Ireland, other than that they came from four northern cities, Falias, Glorias, Murias and Finias, where they acquired their occult skills and attributes. On arriving in Ireland, some accounts state that they burned their boats behind them to prevent themselves from being tempted to return; the Book of Invasions states that they wafted in through the air as a host of spirits. Other sources state that they came from the west (Atlantic Ocean) on clouds.
They then fought two battles, the First Battle of Magh Tuiredh, on the west coast, in which they defeated the clumsy and ill-armed Firbolgs, the indigenous population, and the Second Battle of Magh Tuiredh against the Fomorians, after a guerrilla insurrection by the Fomorians. During this battle, King Nuada of the Tuatha de Danaan lost an arm. He was replaced (since he was no longer perfect) by Bres or Lugh. After defeating the Fomorians, the Tuatha de Danaan gave them Connacht and there was some intermarrying. Nuada had his arm replaced by a silver one (made by Dian Cecht) and took back the throne after Bres was exiled for his tyranny. Balor, the god of death, then killed him.
A third battle was fought against a subsequent wave of invaders, the Milesians, from Spain (who are thought to have been the Celts), led by King Milesius, who overcame the goddess, Eriu whom the Tuatha de Danaan sent against them. The Milesians were magnanimous in victory and named the island Erin, the dative form of her name, in her honour. Defeated, the Tuatha were led underground into the Sidhe mounds by The Dagda. Afterwards, they occasionally intervened in human wars on the side of justice and righteousness, armed with invisibility, flaming lances and magical white shields.
The Tuatha de Danaan fought against the witch Carman and her three sons.
Tuatha de Danaan: