Career
In some sources he"s called Teodor, Fedko or Frederic. In 1386 Grand Duke of Lithuania Jogaila granted him possession of Ostrog castle and appointed him governor of Volhynia with the capital at Lutsk in 1387. In addition to Ostrog, Feodor became owner of Korets, Iziaslav (Zaslav), and other towns.
The Crooked Castle was captured and its commander, Karigaila, brother of Jogaila, was killed.
The Upper castle, with Polish staff and lower, commanded by Feodor, were rescued. He fought in the Battle of Ústí.
A folk song about this battle mentions Frederic, Ruthenian Prince of Ostrog, who left home and had assimilated Czechoslovakian habits and language (January Długosz book XI, page 650). Długosz, however, mentions lieutenant
At Easter of the same year a group under the command of Frederic Prince of Ostrog, Jakub Nadobny from Rogów and January Kuropatwa from Łańcuchów Średniawa, attacked Jasna Góra Monastery, plundered it and destroyed Icon of Black Madonna of Częstochowa.
A year later with Sigismund Korybut he attacked the Hungarian monastery in Lechnica. In the 1430s he supported Grand Duke Švitrigaila and the Teutonic Order in the civil war against Sigismund Kęstutaitis and war against Poland. On 30 November 1432 he was defeated at Kopestrzyn (or kopersztyn) by Ruthenian voivode Wincenty z Szamotuł, Feodor escaped.
After he captured Jasieniec on 13 September, a three-month armistice was agreed.
On expiry of the truce, Ostrogski burned and looted Brest-Litovsk. Castle was not captured, however, due to Masovian Dukes relief.
At that time he was probably imprisoned with Teodor Korybut by their own suzerain, Švitrigaila, and then rescued by Michał Buczacki. lieutenant is not certain if Feodor Ostrogski switched sides and because of it was imprisoned, or if it happened after he was recaptured.
He died as a monk and was buried at the Kievan Cave Monastery under the name Teodosii (Teodor) and was later canonized (his feast day is 24 August).