Tuatha Dé Danann

The Tuatha Dé Danann — the peoples of the goddess Danu, or more precisely the peoples of skill and craft — arrived in Ireland, according to the mythological cycle, in a cloud of mist from the northern islands of the world, where they had learned their knowledge in great cities. They were the fourth of the mythological invasions of Ireland and they came to stay, at least for a time.

They brought four treasures: the Lia Fáil, the Sword of Lugh, the Spear of Lugh, and the Cauldron of the Dagda. They fought two great battles at Mag Tuired — first against the Fir Bolg, then against the Fomorians — and won both, establishing their rule over Ireland. Their king, Nuada, was wounded and restored; their champion, Lugh, killed the monstrous Balor of the Evil Eye with a sling-shot. For a time, Ireland was their world.

When the Gaels arrived under the sons of Míl, the Tuatha were defeated not by force but by negotiation and magic. They retreated underground, into the hollow hills — the sídhe — and became the people of the mounds. In this form they continued to interact with the human world, now as the aos sí: the fairy people whose mounds must not be disturbed, whose paths must not be blocked, and who can be generous or terrible depending entirely on whether you have shown them the respect that was once owed to gods.