Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Vai vilas was a Lithuanian noble and sometimes is considered as one of the sons of K stutis, Grand Duke of Lithuania. In 1358 K stutis and Masovian princes formed a commission to settle border disputes. The Lithuanian side was represented by Vai vilas (Woyszwylt), Patirgas, possibly another son of K stutis, and Eik is, son of Karijotas. This leads historians to believe that Vai vilas ruled some area bordering Masovia. In 1367 a treaty with Livonia mention Vai vilas as Waysewist. Later he is found in Lahojsk, now Belarus. There are theories that an unnamed "nobilis satrapa" who died at the Battle of R dava in 1370 was Vai vilas. He probably died before 1385 or 1387 because he is not mentioned during turbulent civil wars between Vytautas the Great and Jogaila.