Sigismund is a Polish prince who has spent his entire life cruelly isolated in a mountain prison. Imprisoned by his father since infancy due to an astrological prophecy, he lives out his days with only his jailer, Clothold, for company. He possesses a deeply philosophical mind and frequently questions why human beings are denied the basic liberties granted to wild animals.

Rossaura is a courageous young woman traveling to Poland to avenge a personal dishonor. She disguises herself as a man to travel safely with her servant, Bugle, leaving her homeland to seek out the man who abandoned her. Upon discovering Sigismund's prison, she demonstrates immense bravery and later secures a position at court under the alias Astraea to get closer to her target.

Clothold is a trusted royal servant tasked with acting as Sigismund's sole tutor and jailer in the wilderness. He struggles to balance his sworn duty to the Polish crown with his personal sense of honor. When he confiscates Rossaura's sword, he recognizes the weapon and makes a sudden, secretive decision to protect her rather than executing her for trespassing as the law requires.

King Vasily is the aging ruler of Poland and an avid student of astrology. Driven by a prophecy that his newborn son would bring disaster to the kingdom, he faked the infant's death and locked him in a remote tower. He governs largely through superstition and attempts to control destiny by orchestrating a secret test to determine if his son is fit to rule.

Aistulf is the Duke of Muscovy and nephew to King Vasily. He aggressively courts his cousin Stella in an attempt to unify their claims to the Polish throne. Despite his sweet words and flattering gestures, he secretly wears a locket containing the portrait of another woman, raising heavy doubts about his character and romantic sincerity.

Stella is a princess of Poland and niece to King Vasily. She is a direct candidate to inherit the throne and views her cousin Aistulf's romantic advances with sharp skepticism. She intuitively recognizes that his affections mask his political ambitions, actively demanding the truth about the locket he keeps hidden.

Bugle is Rossaura's servant who accompanies her on her dangerous journey to Poland. He provides continuous comic relief to offset the heavy, dangerous situations they encounter in the wilderness. Despite his self-professed cowardice and loud complaints, he faithfully remains by Rossaura's side as they investigate the mysterious tower.