The snappily-dressed Duke of Baloni was once the second-richest duck in the world, seemingly having inherited and fructified a sizable family fortune. It is unclear if his noble family had any connection to the now-defunct nation of Balonia.
In 1953, he visited Duckburg. Coincidentally, Donald Duck had fashioned himself a 'foreign businessman' costume and persona (as part of a con on his uncle Scrooge) that happened to greatly resemble the Duke. This led to Donald's stratagem working better than expected as Scrooge "recognized" him as the Duke of Baloni and tried to talk business with him. Donald's trickery was eventually exposed when the Duke came to dine at the Duckburg Ritz where Scrooge and Donald already were.
Some time after these events (which were the last time Scrooge and Baloni interacted for decades), the Duke was recruited into the Horde of the Violet Hare, nominally as "Haremaster 4 3/4", though in truth the Hares simply needed a wealthy follower to finance their worldwide wrongdoings. This went on for several years until the Baloni fortune was reduced to less than a million; having come to rely on Baloni's seemingly unlimited funds, the Horde was taken by surprise and were forced to shrink back the span of their operations, dismissing many brainwashed followers after wiping their memory of their times in the Horde.
The Duke was one of them, though his brainwashing was even more flawed than the rest, and he thus managed to retain his memories of his Haremaster stint. Like the other Hares-emeritus, he retained a compulsion to look for Atlantean ruins and to partake in secret-organization-like activities, but was able to recognize these strange impulses for what they were, channeling them harmlessly into an online baloney-appreciation club he dubbed the Secretive Baloney Club — though its members still retained a tendency to go snooping around any news of Atlantis, without even really knowing why.[UNOFF]
Behind the scenes
Being the first character introduced as the "world's second richest duck" (prior to the creation by Barks of Flintheart Glomgold or even John D. Rockerduck), however, he retained some limited fame in the fandom, and made an appearance in the unofficial comic story Hare-Brained Hooligans in 2018, which posited an explanation for his disappearance from the comics through the narrative of his joining the Horde of the Violet Hare and going nearly bankrupt as a result. The story reveals his full name as "Torcivio Castellan De Baloni" — Torcivio and Castellan being nods to Joe Torcivia and Casty, the latter being the creator of the Horde in the first place, and the former the owner of the blog on which the mythos of the Horde-copycats was developed in the late 2010's.