Mephitist Empire

In both The Winterbough Saga, and The Ballad of Adler Young, the principal governing realm of the land of Faerie.

It is described by Westersloe Winterbough V (in "From Whom All Blessings Flow," Chapter A) as comprising "some millions of square miles," including most of Faerie. In "The Thin Line," there are descriptions of a great map in the Hall of Statecraft that shows the relationship of the Empire to other realms of Faerie, such as protectorates (e.g., the United Cities), allies (e.g., the Principality of Kennelford), dominated realms (e.g., the Republic of Vulpitania), and enemies (e.g., the Grand Duchy of the Grey Horde).

The term "Empire" is sometimes used to refer to all of the lands ruled by the House of Irenaeus, though as a technical matter, certain lands within the Empire are legally held directly by the House of Irenaeus, in their capacity as the High Kings of Albric Tor. Lands not owned by the High King are considered "Imperial." Hence why many institutions are referred to as "Imperial and Royal," such as the army and the postal service.