The Three-headed Dragon is one of two major villains from the adventure video game King's Quest III: To Heir is Human. It is a monstrous beast that demands the sacrifice of a maiden. The other major villain is the wizard, Manannan.
The Three-headed Dragon somehow took refuge in Daventry, while scorching the land in the process. In order to protect themselves from the creature, the king and queen offered their only daughter to be his demanded sacrifice. Rosella was not scared of the event, as she knows that someone might come and save her.
years later, Alexander finally came to Daventry and put an end to the dragon by summoning a thunderstorm spell, which caused large bolts of lightning to zap the dragon, killing it and ending its reign of terror. Rosella was later freed and both were reunited with their parents.