Redanian Secret Service is one of the finest intelligence agencies in the known world (next to the Nilfgaardian and Koviri intelligence agencies). It is headed by Sigismund Dijkstra of Tretogor. They lease quarters on the top floor above the vice-chancellor's offices at Oxenfurt's Academy, which Dijkstra likes to call the "Faculty of Most Contemporary History" while Dandelion likes to call it the "Faculty of Comparative Spying and Applied Sabotage".
After the death of King Vizimir, the head of the secret service became one the most powerful position in the country, making Dijkstra the real power in Redania. His primary base of operations was in Tretogor, but another facility under his control was Drakenborg castle, where "enemies of Redania" were executed.
Dijkstra was very crafty and the service had extensive knowledge of Nilfgaardian troop movements, as well a good deal of useful information on rulers of both the North and South. An extensive communications network between agents greatly facilitated this. Within Redania, the secret service was generally loathed and feared - mainly because of their reputation for frequent executions of those deemed to be traitors and spies, even though the vast majority of them indeed were spies and traitors.
- The book Shadow People, or the story of His Majesty's Secret Service describes the history of the Redanian Secret Service. It is also featured as a book within The Witcher.