 But from 849 on, when Columba's relics were removed in the face of Viking incursions, written evidence from local sources all but vanishes for three hundred years.The sources for information about the Hebrides and much of northern Scotland from the 8th to the 11th century are thus almost exclusively Irish, English or Norse.The main Norse text is the "Orkneyinga Saga", which was written in the early 13th century by an unknown Icelander.