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.
A race of beings actually IS invunerable while in adolecence. They age, but cannot be killed. A miniority of the race (1 in 20) does not become invunerable, but rather becomes immortal at some point in thier adolecence, and ceases aging while being vunerable to death in all the normal ways. Another minority (also 1 in 20) Permanatly becomes invunerable after adolecence, but ages twice as fast as the race normally does. There is no known way to test for which of the three traits an individual manifests and the three traits cannot mix, as they are tied to the same gene, as it were.