The Barony of Akova was established ca. 1209, after the conquest of the Peloponnese by the Crusaders, and was one of the original twelve secular baronies within the Principality of Achaea. Along with the Barony of Patras, Akova was one of the two largest and most important baronies of the Principality, with twenty-four knight's fiefs attached to it. The barony's capital was the fortress of Akova or Mattegrifon ("Kill-Greek", "Grifon" being a French term for the Greeks) built on the mountainous area known in the "Chronicle of the Morea" as Mesarea, separating Elis from Arcadia and dominating the upper valley of the Alpheios river, by the baronial family of de Rosières, of Burgundian origin.