Derro was a male Ferengi who, as of 2379, served as the Ferengi Ambassador to the United Federation of Planets. At a diplomatic cocktail function in Luna's Lunasphere Artemis, Ambassador Derro tried to sell Federation President Min Zife on his idea to "modernize" the Federation economy. (TNG novel: A Time to Heal)
Derro continued to promote his economic ideas to Zife's successor, Nanietta Bacco. During the Borg Invasion of 2381, Derro was one of nine ambassadors present at an emergency summit on Earth, where Bacco attempted to gain allies in the defense of local space from the Borg Collective. Derro initially abstained, though Bacco convinced him to have the Ferengi join the expeditionary force.
Bacco later invited Derro to a private meeting, asked the Ferengi Alliance to purchase Breen mercenaries to join the allied fleet, and thus prevent the Tholian Assembly from doing so. The combination of her proper Ferengi greetings, her offerings of gree worms, tube grubs, Kytherian crabs and Slug-o-Cola, and her ability to win over the Gorn Ambassador Zogozin convinced him to present the option to the Grand Nagus. (ST - Destiny novel: Mere Mortals)
After hiring the Breen, Derro also attempted to sell them weaponry; however, he was outbid by another weapons merchant, Sekki. Because of this history, Derro was willing to reveal Sekki's location to Professor Sonek Pran, who was investigating the sabotage of the Federation's post-recovery efforts.
- It is unclear to whether Derro's debt was to Ezri herself, or one of Dax's previous hosts.