Fomorians

The Myth
“The tribe of the Fomorians was on the scene long before any other races came to Ireland. However, the Fomors lived mainly in the sea. The first outside race to invade Ireland was the race of the Partholon; very little is known of them. After 300 years of struggle against the Fomors, the Partholons died of an epidemic.
Next came the race of Nemed who also suffered from an epidemic. This time, though, some of them survived, only to be oppressed by the Fomors.
Later came colonizers from Spain or Greece called the Fir Bolgs. They were actually three tribes; men of Domnu, men of Gaillion, and men of Bolg. They inter-married with the Fomors and held the country until the arrival of the “Tuatha De Danann”.
Source: (from Ancient and Shining Ones – by DJ Conway)