Karel

カレル, Sword Saint,Saint of Swords,Sword Demon

It is pointless to marvel over one's power. That is not the kind of strength I seek.
— Karel to Fir, in Fire Emblem: The Binding Blade

Karel (Japanese: カレル Karel) is a recruitable swordmaster in Fire Emblem: The Binding Blade and Fire Emblem: The Blazing Blade. Acting as among the few characters that are playable in both The Binding Blade and The Blazing Blade, Karel undergoes a radical shift in personality between games, going from a murderous warrior to a calm, indirect mentor. In both games, he is more well-known by his nickname (either The Sword Saint or the Sword Demon), and he is considered one of the best swordsmen in all of Elibe.

(Source: Fire Emblem Wiki)