The Tyranny of the Barons is the name given to the period of Oceanan history from 1257 until 1456, in which the central authority of the crown broke down after Turbo III died without a legitimate heir, ending the de Calvadoux dynasty of the conquering Neustrians. In the wake of this, the Parliament of the Gryoch Fields was held by the noble families in order to select a new king, but the families were unable to agree on a suitable candidate. In an attempt to force the matter, Baron Aidoch Traquair of Peidha, a noble of relatively low rank from the powerful Traquair family, seized the opportunity, raised an army, and took Emporium, becoming Adoxus I.

Although some noble families swore fealty to the new king, many refused to assent to what was seen as a naked power-grab, beginning a protracted, multi-sided and bloody struggle known as the War of the Forty Families, a conflict which outlasted Adoxus' 29 year tenure on the Oceanan throne. Further conflicts raged between the nobility throughout the period, such as the War of the Bastard, the War of the Regency, and the Struggle through the Long Night as the king was often a figurehead who could not command any effective power outside of Emporium itself. Regional wars and petty struggles for territory were common, and a breakdown in law and order was generally evident. The period is generally considered to have ended when Flanarghas MacDubh, Duke of the Upper Hermisna defeated King Turbo V at the Battle of Starybridge, becoming Panurgus I of Oceana and curbing the powers of the barons.

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