The path to becoming a Dragon King has been laid before Noah. How to devour the world, from initially inciting war, weakening all parties, to massacring billions of living beings, weakening the World Will, and finally tearing the world apart, devouring its essence, and ascending to the title of Dragon King, Noah has mastered all the details.
If there hadn't been a moment of temptation, it would be a lie. That is truly immortality, needing no reliance on external objects, nor faith. Even if the world is destroyed, one would still persist, unscathed.
What is most tempting is that the current Noah already possesses the power to initiate a world-ending war, even though he is in a medium-large Material Realm that is quite developed, with great potential.
