Eustace, the Black Monk

"No one can live for a long time who has bad intentions all his days."

So ends the 1284 verse drama, mostly fiction and fancy, based on the tumultuous and violent life of the former Benedictine monk Eustace, son of the lord of Boulogne.  He was, as they say, bad as he wanted to be.
He served no master, king or God with any faithfulness.  It is said Eustace studied black magic in Toledo, Spain, before entering a monastery in Calais where he was known for his swearing and gambling, not his piety.  He left to avenge the murder of his father when about twenty, but the matter came to a duel which his champion lost; his adversary was then considered innocent.  With no prospects for justice, he somehow crossed the Channel and met King John of England, who must have been impressed, for the King gave the adventurer command of thirty ships to attack his former possessions in Normandy.  Losing John's support, probably due to intrigue by his enemies in Boulogne, his status changed from King's man to pirate.  He and his brothers established bases on the Channel islands of Guernsey and Sark, raided and plundered, and the Robin Hood-like legend grew.  Rumor had it that Eustace had made a pact with the devil to render his ships invisible, that he was capable of shape-shifting and employed impenetrable disguises.
When the French ejected him from the islands, he went over to their side.  Taking advantage of civil war in England in 1215, Prince Louis attempted an invasion to claim the throne the following year, sailing in one of Eustace's ships.  It failed, and in a second expedition the English attacked fiercely, boarded the flagship, and beheaded the Black Monk then and there.  A subsequent treaty required Louis to give up his claim to the English throne and remove Eustace's brothers from their lairs on the Channel Islands, which passed to English control.
Five hundred years later, the pirate Blackbeard had a quite similar life and death.  Had the Black Monk returned?