User blog comment:Bluebeard2/Philosophical discussion concerning the nature of Necrons and Tyranids/@comment-2253300-20111018005329

Actually Necrodermis is an organic metal alloy. Still good point. Also the Necrons would go after the Tyranids because the Tyranids want to depopulate the universe. Essentially the Tyranids are taking all of the C'tans' food.