They were sent here to fight, having faith in the Constructor's plan, but Nature was invincible from the start, and the only one that received instructions about this was Edward.
For that reason, he was afraid at first when he saw what was really needed. Now he understood why the Constructor had so many secrets; it was needed because not everyone would act as they should knowing about this.
Life and death became part of Nature and the rest of the world once she created Zelhart and Hulum Ying. Still, Nature couldn't be killed since she created Zelhart in a way that prevented death from directly touching her, and even if they managed to kill her, she would just reincarnate at another creature, simply any creature. Yet, Zelhart was the key, being a Rebis with her own living feeling, controlling death, and maintaining Nature's creation far away from her even though it was not done on purpose.
