House of Kostka of Postupice
It is possible that Vok of Sovinec intended to create a vast enclave along the Bečva River, which would include Helfštýn, but he never succeeded in materialising this idea.
In 1467, he sold the castle and domain for the impressive amount of 30,000 Hungarian guldens to Albrecht, Zdeněk, and John Kostka of Postupice, and George of Landštejn. During the Hussite movement, but in particular during the rule of George of Poděbrady, the House of Kostka moved among the most important noble families thanks to their possessions and political influence. They stood unwaveringly on King George’s side in 1467, and during his campaign in Moravia in 1468, Hungarian King Matthias Corvinus tried to conquer Helfštýn as a lynchpin of the Poděbrady side. The castle was damaged during the siege, but no mention has been preserved that the Hungarians succeeded in capturing Helfštýn. In 1468, Zdeněk Kostka fell in battle against the Hungarians in northern Moravia, and soon after that, Albrecht Kostka began to vacillate in his loyalty to King George, coming over to Matthias’ side in 1470 and becoming his confidant. At the time, he was the sole owner of Helfštýn, and after acquiring in 1470 the Přerov and Hranice domains from Ctibor of Tovačov and Cimburk, he apparently intended to establish a larger complex of domains in Moravia under Matthias’ protection. But this intention was not realised, and political relationships with the Hungarian court forced Albrecht Kostka to sell his domains along the Bečva River to William of Pernštejn. First, Helfštýn in 1474, and Přerov and Hranice a year later. A new era came to Helfštýn Castle, during which it was extensively rebuilt.