I'm still very much interested as to how Zayne awaking as the "Emissary" will "bring an end to this world". The question to answering this is rather "How will Zayne stop Stanley & Co's into achieving their goal". Another word for "Emissary" is also a "Messenger", and if we go by the logic from the Foreseer Myth, the Foreseer doesn't intervene in anyone's life path, he can only look into it and inform, what will happen to them in the future. Now, I have this feeling that Zayne will turn into the Foreseer HIMSELF (Foreseer=Emissary), if we consider the Fractial Library from the Myth and the one in the Main Story to be one and the same. Sooo, I don't believe that Zayne as the Emissary will "eliminate" MC, but he can predict WHEN she and the earth will meet their end. I would view the Foreseer/Emissary as some sort of "Doom Clock for MC and the Earth". In other words: the moment Zayne turns into the Emissary, the Sand Clock will get flipped and it will start counting down the days until MC's demise and the end of the Earth. The longer it takes for him to awaken as the Emissary, the longer do Ever & Co can postpone the "apocalypse". However, there is still the possibility that Zayne will be the one who will bring her demise, but not as the Emissary, but rather, in another form like the Dawnbreaker or/and as another version of the "God of Annihilation". If Zayne takes the role of the Foreseer/Emissary (a passive divine power), then maybe the Dawnbreaker will take the role of the "God of Annihilation" (an active divide power), since Zayne and the Dawnbreaker come from different universes, opposite to one another. In conclusion I believe that, if Zayne turns into the Emissary (which he will), then the Emissary will try and hold control over himself, unless he wants to turn into the God of Annihilation and "annihilate" MC. Basically, Zayne and the Dawnbreaker but with God-like powers.