It was the custom of ancient bards to utter an imprecation or “satire” against those offending them.[161] The irate fasting and cursing by the Irish clergy was a thinly Christianized continuation of the same Irish habit, inspired by the same Irish temper. There was no chasm between the pagan bards and the Christian clergy, who loved the Sagas and preserved them. They had also their predecessors in the Druids, who had performed the functions of diviners, magicians, priests, and teachers, which were assumed by the clergy in the fifth and sixth centuries.[162] Doubtless many of the Druids became monks. Christianity came to the Irish as a new ardour, effacing none of their characteristics. Irish monks and Irish saints were as irascible as Irish bards and Saga heroes. The Irish temper lived on in St. Columba of Iona and St. Columbanus of Luxeuil and Bobbio. Both of these men left Ireland to spread monastic Christianity, and also because, as Irishmen, they loved to rove, like their forefathers. Christianity furnished this Irish propensity with a definite aim in the mission-passion to convert the heathen. It likewise brought the ascetic hermit-passion, which drove these travel-loving islanders over the sea in search of solitude; and so a yearning came on Irish monks to sail forth to some distant isle and gain within the seclusion of the sea a hermitage beyond the reach of man. There are many stories of these explorers. They sailed along the Hebrides, they settled on the Shetland Islands, they reached the Faroes, and even brought back news of Iceland. But before the seventh century closed, their sea hermitages were harried by Norsemen who were sailing upon quite different ventures. From an opposite direction they too had reached the Shetlands and the Hebrides, and had pushed on farther south among the islands off the west coast of Scotland. So there come sorry tales of monks fleeing from one island to another. These harryings and flights had gone on for a century and more before the Vikings landed in Ireland, apparently for the first time, in 795.[163] There followed two centuries of fierce struggle with the invaders, during which much besides blows was exchanged. Vikings and Irish learned from each other; Norse strains passed into Irish literature, and conversely the Norse story-tellers probably obtained the Saga form of composition.