Casca is a former unit commander of the Band of the Falcon and an estranged companion of Guts.
Originally a callow peasant girl living in a remote mountain village, she develops into a capable warrior upon joining the Band of the Falcon and aids greatly in the group's storied successes during the Hundred-Year War. Following Guts' departure and Griffith's subsequent imprisonment, she is forced to assume the position of the band's leader, succeeding in preventing the complete annihilation of the Band of the Falcon and rescuing Griffith from the Tower of Rebirth. Crippled from his year-long torture and demoralized by his fall from grace, Griffith ultimately invokes the Eclipse, in which he is reborn as the fifth God Hand member Femto and rapes Casca. Having physically survived the ordeal, she regresses into an infantile and largely mute state.
In order to restore Casca's fragmented mind, Guts and his traveling party journey to Elfhelm. After Schierke and Farnese take part in the Corridor of Dreams ritual conducted by the Flower Storm Monarch, Casca is mostly restored to her prior mental state. However, she now suffers from crippling panic attacks whenever she sees Guts face-to-face and recalls the trauma of the Eclipse.