Kelemvor suffered from a form of lycanthropy that had been passed down through his paternal family. Kyle Lyonsbane, Kelemvor’s grandfather, was a mercenary ruthless in extracting payment, and who had also left his sorceress companion on the battlefield to die so that he could plunder the enemy’s stronghold. In her last breath, the sorceress bestowed a curse upon Kyle. Afterward, Kyle could never attempt to perform an act for any type of reward without turning into panther, and return to his human form only by taking a life. Under the curse, only unselfish and heroic acts were permitted. A mirrored form of the curse was passed on to Kyle’s son, making him unable to perform any act without asking for a reward, or suffer the same metamorphosis.
Kelemvor Lyonsbane was the seventh descendant of Kyle. Because of the curse, Kelemvor had become a panther and mercilessly killed his own cruel father when trying to protect an innocent house maiden. After this, he left his household to become a mercenary, hoping to find a release from the curse.