Eustace the Monk

The Monk was a mysterious hooded figure active in the Caribbean Sea around 1717. Seeking informations and merchandises, the man often tasked the pirate Alonzo Batilla with finding crates protected by powerful warships.

Trivia
Never revealing his identity to Batilla, The Monk, however, give some clues to the frenchmen over the course of their meetings. Mentioning a raid on Normandy at the head of thirty ships or his presence at the Battle of Sandwich, The Monk appears to be Eustache Busket, also known as Eustace the Monk, a french nobleman-turned-pirate who lived in the XIIth century. It's not known, whether The Monk lied about his identity or Eustache had actually found a way to extend his natural lifespan by unknown means.

Reference

 * Assassin's Creed: Pirates