He plays a big role in The Secret of the Black Mace, the main quest for the Cossack Hetmanate. He mysteriously knows a lot about the Black Mace, including its location. He uses the character to help him become King of Poland in return for helping the character find the Black Mace.
He is based on a real person, Janusz Radziwiłł (1612–1655), who was a Polish-Lithuanian noble and one of the most powerful people in the Commonwealth, holding several administrative titles such as Field Hetman of Lithuania. However, he later sought to overthrow the Commonwealth government and collaborated with the Swedes during their occupation.
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Janusz Radziwiłł (1612–1655)