Celtic mythology - the last of 5 successive mythological peoples who invaded Ireland, the "people of the goddess Danu", a race of divine beings who inhabited Ireland before the Celts. They fought 2 battles, first the prior invaders, the Fir Bolg and then the Formorians, in the 1st and 2nd Battles of Magh Tuiredh, using 4 powerful talismans which aided them in battle:
The De Dannan were skilled in magic and druidic lore. Their chiefs evolved into many of the gods and goddesses of the Celtic pantheon.
Eventually, these divine beings were defeated by the Mileseans, and retreated to the Otherworld, that being the lower half of Ireland represented by sidhe. In timeless beauty.