Board Thread:Spoilers!/@comment-25361971-20150928100931/@comment-25926288-20151001012057

If the Darkness is set free, whether by the speculative TLK or by the method shown before, it will destroy everything.

Emma was the one to tether it because she had the dagger in her hand and she's the leader of the group and the most powerful amongst them.

The plot explanation on that page is incorrect or we just don't know. The Darkness clearly tried to kill the Apprentice so it might would have killed Regina too. So, either way, Emma was saying that Regina came to far to either die or to be right where she started or worse.