that maybe the sword will kill the darkness inside of Emma to help the balance of light and dark be restored (or to help her perform a huge task).
which theoretically should not be there since Snowing cast out all her darkness when she was a fetus in the womb?
Dark One Curse?
Still may have some remnants in there.
Past darkness leave a mark. Regina’s heart is an example. Couldn’t quite tell but Snow’s/Snowing’s heart might be another.
I think my theory is sound. And the writers don’t follow their own rules much anymore so if Snow’s heart was meant to be healed and Regina’s not then it doesn’t surprise me.
Anyway, I have sort of (but not completely) changed my mind after watching the previous episode.It seems that Emma’s new nemesis is Gideon (and maybe Jafar later on) rather than the queen, so perhaps the sword can only be used by the hero to kill their villain or vice versa. In which case, Rumple had the sword the whole time and it could have been very useful in getting rid past villains, such as Pan *fume*
Or maybe the old savior needs to die for a new one to appear.
Keeper of Regina's bravery