An atmosphere of magic and mystery surrounded the Tuatha Dé Danann. We read that they first came to Ireland in obscure clouds, landing on a mountain in the west of the country, and that they caused an eclipse of the sun which lasted for three days. They brought with them the Lia Fáil (Stone of Destiny) which cried out at Tara when touched by the rightful king, the great spear of Lugh which guaranteed victory to its wielder, the sword of Nuadhu from which no opponent escaped, and the cauldron of the Daghdha from which no company departed unsatisfied.
After their defeat by the Gaelic people, an agreement was reached whereby the Tuatha Dé left the upper half of the ground to the Gaelic people and they themselves went underground to live in the ancient barrows and cairns which dot the landscape. It was said that they ‘used to fight with men in bodily form, and used to show delights and mysteries to them, and people believed that they were immortal’.
The oldest and most venerable member of the Tuatha Dé was the Daghdha. Later his son Bodhbh Dearg became king of the Tuatha Dé, and the great phantom mariner Manannán divided the ten principal otherworld dwellings among their chiefs. Their dwellings within cairns and raths have beautiful halls and rooms, extremely bright and with golden and silver trappings and decorated with wonderful gems and jewels. They have great feasts there, with fine food and drink, and exquisite music of harp.
It was Manannán, too, who instituted the féth fiadha (‘cloak of concealment’), an obscure magical device which enabled the Tuatha Dé, when they so wished, to become invisible to the human world. He also arranged that they would have magical swine, which returned to life after being killed so that the warriors could again hunt them. As well as dwelling in cairns and raths and in wild parts of the Irish landscape, the Tuatha Dé sometimes went abroad to reside in idyllic overseas realms such as Magh Meall (‘the Delightful Plain’) or Eamhain Abhlach (‘the Region of Apples’), which is cognate with Avalon, which surfaced later in Arthurian romance.