"Duc De Richelieu" is a specific title that refers to a French nobleman named Armand Emmanuel Sophie Septimanie de Vignerot du Plessis, who was a prominent figure in the country's history during the 18th century. Some synonyms for "Duc De Richelieu" could be "French nobleman," "rich and powerful aristocrat," or simply "duke." Additionally, one could use the title "Marshal of France" to refer to Richelieu's military career or "Prime Minister of France" to denote his political influence. Overall, "Duc De Richelieu" is a distinct title that signifies a prominent figure in French history, and there are several ways to refer to him using related terms and titles.