The Sphere of Expansion and Diplomacy, which was also referred to as the Ministry of Expansion and Diplomacy or the Pyramid of Expansion and Diplomacy, functioned as one of the twelve Spheres of Influence within the structure of the Sith Empire. A Dark Councilor presided over this Sphere, which held the duties of managing the Empire's territorial growth and overseeing all diplomatic interactions. The Imperial Diplomatic Service reported directly to the Sphere's leader, a role occupied by Darth Ravage during the era of the Cold War.
Following the Sith Empire's loss to the Eternal Empire, Empress Darth Acina merged this sphere with the Sphere of Imperial Intelligence, creating the Sphere of Galactic Influence.