The first inhabitants of Ireland after the last ice age, they were the remnants of surviving hunter/gatherer tribes of the ice age.
The thawing of Ireland left the Fomorians isolated from Britain. With plentiful food and a low population they never attempted to leave and instead were invaded regularly.
The Fomorians ate seafood, birds, wild boar, and hazelnuts.
Spears, arrow, and Harpoons were used, shelters were temporary and hearths were outdoors. The invading Tuatha de Danaan would hold that they were superior at magic, however, suggesting that they had a superior understanding of nature or medicine.