Fir Bolg

the Fir Bolg were an ancient race of Irish invaders descended from the Nemedians. They conquered Ireland from the Fomorians, and split it into five provinces - Connacht, Leinster, Ulster and North and South Munster. They ruled as High Kings of Ireland for 37 years, with nine reigning kings, before the Tuatha Dé Danann invaded and contained them in Connacht, defeating them at the First Battle of Magh Tuiredh. The Tuatha Dé Danann then reigned over Ireland.

Origins
Nemed and his followers, the Nemedians, sailed to Ireland but, upon arriving, were persecuted by the Fomorians. The Nemedians sailed back to Greece, where they came from. However, after 230 years, some of his descendants sailed back to Ireland and conquered it., they became the Fir Bolg, or "men of bags", because they carried bags of clay.