Ringtail Van Dukke (known as Deckselsen Duck in the original Dutch) was an anthropomorphic duck who then was, for some time, a ghost.
After a life of wanton piracy and murder, this ancestor of the Duck family took advantage of a royal pardon to turn himself around and become a honest merchant (despite the distrust of the public and the ire of his even more bloodthirsty nephews and wards, Gruffy, Ruffy & Tuffy). However, a group of piratical Beagle Boys (known as the Van Biegel Lads), whom he had hired as his crew, stole the first shipment of gold he was carrying, for his uncle Pinchpenny Van Dukke.
Ringtail spent the rest of his life, and afterlife, trying to reclaim the treasure and fulfill his oath to Pinchpenny. At some point, he als wrote an autobiography which found its way to the Duck Family Archives in Scrooge McDuck's Money Bin. Finally, in 1992, Ringtail finally located it with the help of his descendants Huey, Dewey and Louie Duck and Donald Duck (it had in truth been hidden beneath the hull of his own ship by the Biegels, who had never been able to retrieve it). Having fulfilled his promise by returning the money to Pinchpenny's heir Scrooge McDuck, Ringtail moved on from the living world, not before a final goodbye to Donald inside a spookhouse!
Behind the scenes
Ringtail Van Dukke is central to the 1992 story The Last Voyage of Ringtail Van Dukke.
It is not altogether clear what side of the Duck family is he related to; in the original version of the story, his last name is Duck, as opposed to Van Dukke, suggesting he is an ancestor of the Duck family rather than the McDuck clan. However, his uncle Pinchpenny is explicitly identified as an ancestor of Scrooge McDuck's.