Eriu is an ancient land. First settled some 10,000 years ago, it was settled around 700 BC by the Gaels, a Celtic people. For over a thousand years Eriu had little contact with the rest of the world, save for a small amount of trade with Albion, until Saint Patrick began the large-scale Christianization of the Gaelic kingdoms in the 5th century AD. During the Dark Ages following the fall of Roman authority in the West, Eriu became a centre for Latin and Greek learning and even sent missionaries to convert the other pagan peoples of northern Europe to Christianity.
Eriu itself however only became involved with the the wider world when it came to be attacked by the Vikings. Norse jarls established their own kingdoms around the cities of Dublin, Cork, Waterford and several others, and subsequently recruited Erians into their armies overseas. Erians made up a significant proportion of the initial settlers of Iceland and Greenland, and it is said that the first European child to be born in Vinland had Gaelic ancestry.