The weapon has elvish writting on the hilt, which describes the power of the blade and a warning to whomever may use it. the main users are elvish warriers and members of a royal family as it is normally handed down a family line. The blade is made of platinum which shines mother of pearl and when commanded to it can submerge itself in boiling water which can get up to 110 degrees. The attacker can not withstand the blade near them or on there skin, as the blade enters the body the boiling water will burn them from the inside out within a matter of seconds.
How about a dragon how cheerfully rules over a kingdom; his people all know him for what he is, and dragons are looked upon as wise and benevolent creatures. Dragonslayers from other kingdoms coming to free it from 'tyranny' are likely to get beaten to death by peasants with cast iron skillets.