All of the Baronies are nominally ruled by Mithras of London, though some are more loyal than others. The Scottish Toreador lords and the feral Gangrel vampires of Wales were significant threats to the power structure which Mithras had created, not to mention the Lupines who stalked the countryside.
The fiefs which comprised the Baronies of Avalon during the Middle Ages, as well as their rulers, were:
- The Fief of Carlisle on the English-Scotish border was ruled by the Brujah Baron Nathaniel.
- The Fief of York in northern England was ruled by the Ventrue Baron John.
- The Fief of Lincoln in the English Midlands was ruled by the Ventrue Baron Stephen.
- The Fief of Chester on the border with Wales was ruled by the Ventrue Baron Marcus Verus, childe of Prince Mithras of London.
- The Fief of Gloucester on the southern border with Wales was ruled by the Malkavian Baroness Seren.
- The Fief of Norwich in East Anglia lacked a baron in the thirteenth century and was beset by the Cainite Heresy.
- The Fief of Exeter in England's southwest is ruled by the Ventrue Baron Hugh.
- The Fief of Winchester, located between Cornwall and London, was ruled by the Toreador Baroness Melusine d'Anjou and was also a haven for the Tremere who were frequently at odds with Prince Mithras.
- The Fief of Canterbury in England's southeast was ruled by the Toreador Baron Adrian of Canterbury.
- The Fief of London was the personal domain of Mithras from Roman times to through the early twentieth century.
In addition to these Baronies, the following are vampiric domains which were politically tied to the Baronies of Avalon.
- The Fief of Lothian based in Edinburgh, Scotland was officially a vassal state under Prince Mithras, but the Toreador lords under Prince Robert are effectively an independent domain.
- The Dominion of Uilidh in Ulster, Ireland is ruled by the Brujah Eileen, though its tribute to Mithras is fundamentally protection money to keep the lord of London from interfering in the dominion.
- The Pale was a Cainite political realm as much as a mortal one. The Fief of Dublin, as it was officially known, was ruled by the Ventrue Prince Edward de Warene, the grandchilde of Baron Stephen of Lincoln and supposedly loyal to Mithras.
- The Connachta in the southern portion of Ireland was controlled by a group of Irish Ventrue who were as wild as any Gangrel. Their baron, Rory of Kerry, did not claim loyalty to Mithras but worked frequently with the English vampires.
- The Kingdom of Deheubarth in southern Wales was under the dominion of the Fief of Gloucester and its Baroness Seren who was a Welsh queen in life.
- The dominion of Gwynedd in northern Wales was ruled by Rhodry ap Geraint ap Mithras, grandchilde of the Prince of London. His "uncle" Marcus Verus, baron of the Fief of Chester to the east, kept this Welshman in check and loyal to Mithras.
- The Kingdom of Powys in mid-Wales was ruled by the Ventrue Baron Daffyd ap Bindusarra, whose loyalty to Mithras was tenuous at best.
- , p. 90, 93-96.