The innkeeper's son Johannes Turmair from Abensberg, better known as Aventinus, had an astonishing career. He served at the court of Duke Wilhelm IV as an influential educator of princes. During his time as the official state historiographer, he conducted extensive research in the Bavarian archives and engaged in critical source studies. His works were groundbreaking for modern historiography in Germany. Using expressive colloquial language, he made his knowledge accessible to everyone and described the land and its people so accurately that his texts remain relevant today. The biography sheds light on the life’s work and fate of this significant humanist, who, as a critical free spirit, sought independence but faced considerable challenges in the Catholic duchy.