The King's Dark Lanterns are the intelligence branch of the King's Citadel. Whilst it's existence is not a secret, it is a clandestine organisation and the details of it's operations are kept from the public. Agents of the Dark Lanterns are granted the authority to conduct operations on foreign soil, acting in Breland's interest across the world.
The Dark Lanterns are the most powerful intelligence agency in Khorvaire, funded and supported by the vast resources of Breland and the more public facing branches of the King's Citadel.