One of few characters who has a playable appearance in both titles, Karel's personality drastically differs between the games. [[Karla (Fire Emblem)|] is his sister, Bartre his brother-in-law, and Fir, his niece.
In Fire Emblem: The Blazing Blade, Karel is a bloodthirsty warrior who will stop at nothing to sate his bloodlust, to the point where he is better known by his moniker of Sword Demon. He can be recruited instead of Harken depending on the conditions met during the chapter.
Twenty years later, in Fire Emblem: The Binding Blade, Karel appears as an endgame recruit in Chapter 23, and only Fir and Bartre are capable of recruiting him, convincing Karel to fight alongside his family one more time. Now much older, Karel has significantly calmed down and appears almost as though he were a different person altogether. He serves as a mentor for other characters, and shares a brotherly bond with his brother-in-law Bartre.
Following the end of the Disturbance of Bern, Karel retreats back to his village in Bern, where junior swordfighters learn the path of the sword, guided by his indirect mentoring.
