Sir Swamphole McDuck was an anthropomorphic duck.
The mysterious hood-wearing Sir Swamphole McDuck, born around 1190, was the leader of the Clan McDuck and lived in Castle McDuck. In 1220, he sealed the entrance to the castle's dungeons, arguing that the clan couldn't afford to have working torture chambers anymore. However, it seems Swamphole had ulterior motives for turning the useless dungeons into secret passages, as he went to great lengths to conceal an entrance to the dungeons in the graveyard, with the entrance disguised as his tombstone (while his actual skeleton is in fact hidden inside his armor in the Castle's great hall). Indeed, the dungeons were transformed a few years after Swamphole's passing into the hiding place for the Treasure of the Knights Templar. Swamphole's dubious doings also seem to have been related to the Dismal Downs swamps in some way (as his name implies) that involved diving in them. At any rate, Swamphole died in 1260; his ghost is among the various McDuck ghosts haunting Castle McDuck, and, like the rest of them, he spends a lot of his time playing golf. Possibly due to the sport not having existed during his lifetime, Swamphole is a very poor player and also always forgets to yell "Fore!".
Behind the scenes
His nobility title is changed in the Italian and Danish translations: in Italian, he is a duke, whereas in Danish, he is a baron.