"born in the most obscure spot in England," Wimund was educated at Furness Abbey. He was tall and fair, and had a good speaking voice, but had a proud heart and expected to accomplish great things. He claimed to be the son of the Earl of Moray, which seemed unlikely, but more recent theories are that he was possibly the illegitimate son of Óengus of Moray, who became Earl after Wimund was born, or possibly the illegitimate grandson of King Duncan II.
At some point Furness is asked to create a sister abbey at Rushen on the Isle of Man, part of the Kingdom of the Isles. The well-spoken Wimund was made Bishop of the Isles by Thurstan, Archbishop of York. While bishop, according to Newburgh, at some point he started claiming that he wa deprived of his proper inheritance by the King of Scotland. He gathered supporters, promised them to share in his successes and riches, and embarked on a career of descending on
...the provinces of Scotland, wasting all before him with rapine and slaughter; but whenever the royal army was dispatched against him, he eluded the whole warlike preparation, either by retreating to distant forests, or taking to the sea; and when the troops had retired, he again issued from his hiding-places to ravage the provinces.
Unable to stop Wimund's reign of terror, bought him off by giving him Furness and the territory around, giving him some feudal opportunity to collect taxes, etc. Those who suffered under him, however, did not appreciate this. They waited until they could find him separated from his men, captured him, castrated him, and blinded him.
He was forcibly retired to Byland Abbey, where William of Newburgh resided. He had no regret for his actions, however. In Newburgh's words:
Afterwards he came to us at Byland, and quietly continued there many years till his death. But he is reported even there to have said, that had he only the eye of a sparrow his enemies should have little occasion to rejoice at what they had done to him.
If you want to read his story according to Newburgh, you can find it here.
His success in piracy was probably because his attacks were in the Kingdom of the Isles, a series of locations far enough apart that it wasn't easy for the king to send troops to deal with him, as opposed to on the Scottish mainland. We will look at the geography and history of the Kingdom of the Isles tomorrow.