In early Medieval Europe, a prime subject of frightening tales-come-true were the famously marauding and pillaging Vikings, spilling out of their dragon-headed longships in a state of bloodlust, thirsting for gold. With their menacing presence eventually stretching from eastern Europe and the Mediterranean all the way to North America, no land seemed safe – and it was early on in their globetrotting exercise that the Vikings zoned in on the appealing green shores of Ireland. From 795 CE onwards, monasteries and towns were looted or destroyed in persistent raids, followed by the building of forts and settlements which allowed these Norsemen to become wildcard players on the Irish political scene. The Vikings, although losing their autonomous power in the late 10th to early 11th century CE, had by then already integrated into Irish society through intermarriage and close contact with the locals, and left a lasting mark on both commerce and culture.
This is a companion discussion topic for the original content at https://www.worldhistory.org/article/1162/the-vikings-in-ireland/.