This podcast episode of "The Rest Is History" discusses the 16th-century expedition of Lope de Aguirre, a Spanish conquistador, into the Amazon rainforest in search of El Dorado. The hosts detail Aguirre's brutal actions, including mutiny, murder, and the eventual demise of the expedition. Aguirre's motivations are explored, suggesting a blend of ambition, resentment towards Spanish authority, and possibly a degree of madness. The episode uses historical accounts and sources to reconstruct the events, highlighting Aguirre's letter to King Philip II as a key piece of evidence. The narrative concludes with Aguirre's death and the lingering question of whether his actions were purely driven by madness or had underlying political motivations.