You shall carry your sibling, be his support and guide.
He shall be your shelter, guardian, aegis firm.
United you stand, divided you fall.
Brendan stared at the creature in the pale moonlight, transfixed by the silvery petals that glistened beneath that perfect purity. It was not until his final breath that he gathered his wits enough to scream after the thing had descended on him, all muscle and thorns and hard, barklike skin. It was too impossible, even the crimson blossoms that shone in the light of the moon.
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.