The Firbolg is a race of men,n ot all that different from the tribes that later came to Ireland. They were 4th tribe to invade and try to conquer Ireland for themselves, but their plans was derailed when the Tuatha came. To survive, they allied with the Fomorians to survive, but despite this they failed.
Today the Firbolg remain conquered by the tuatha and none of their original settlements remains in the World. Only in the Overworld their settlements remains unconquered, altough with the rise of the Scion's now that the war between the gods and the titans is drawing closer.
The Firbolg are tougher and stronger thanks to their older heritage, but they lack some of the quick wit and charm of the humans as they are a more primitive sort of human.
Strength +1, Stamina +1, Charisma -1, Wit -1