Non-Imperial realm within Faerie that is referred to in a number of the adventures within The Winterbough Saga. The centre of government is said to be at the "Great Lair," which is situated upon "The High Rock."

The Grand Duchy is first seen in "The Thin Line," as the force battling the Mephitist Empire for control of the United Cities, a small realm allied with the Empire. The Grand Duchy does strike first, seizing control of the United Cities, but in a coup de main formulated by Imperial Marshal Prince Roland, and carried out by Westersloe Winterbough V and Meadow Grainmaster, an operation is carried out which rescues a key official of the United Cities, who promptly invokes the treaty between that realm and the Empire. At the twin battle of Flourford-Mossford, the Grand Duchy's forces are checked thanks to furious resistance by the 37th Regiment, and then sent reeling by a counter-attack launched by reinforcements.

The campaign, in general, appears to have been a serious blow to the Grand Duchy, greatly disorganizing its economy, its armed forces, and its ruling house (since The Great Wolf was killed by Winterbough at Mossford).

In "The Coin of the Realm," the director of the Imperial & Royal Mint shows Winterbough some coinage from the Grand Duchy, noting that it had been debased through the use of base metals, a likely result of the economic turmoil in that realm.

In the adventure "Red Sky at Morning," the Grand Duchy suffers a second check at the paws of Imperial forces, and of Winterbough in particular, as their effort to conquer the Glittering Isle is foiled. One of the lower-ranking princes of the blood, Erik of Vangaria, is captured, and along with the surviving members of his command, are sent as prisoners (the Wolf Prisoners) to Elfhame, where they work on various projects.

Little has been revealed (through October, 2016) about the society of the Grand Duchy, save that it is militaristic and rather cruel. Prince Erik and his wolves are declared dead, for all practical purposes, by the Grand Duchy, and they are not ransomed. The chief form of worship appears to be to a "Great Alpha," represented by a wolf-femme.