Hypatian Codex
Tverai is identified with Tviriment Castle, mentioned in 1251 by the Hypatian Codex. The castle was the fortress where Vykintas, Duke of Samogitia and victorious leader of the Battle of Saule, defended himself against Mindaugas, crowned as King of Lithuania in 1253, during a civil war for power in the early Grand Duchy of Lithuania. Vykintas was defeated and Mindaugas became the undisputeded monarch.