Knight
A Knight is a hero character from The Sims Medieval. Only knights, monarchs, hangmen, and spies can duel. Knights are one of the few hero sims that can travel to other Kingdoms for quests. 
The Knight will need to level up his/her sword to advance in quests. To level up you must duel, which allows you to gain experience.
The Knight's responsibility is to train villiage sims to join the kingdom's army. A kingdom with a strong army will be able to pillage money from other kingdoms, and defend themselves from foreign attacks.