Board Thread:Spoilers!/@comment-2153169-20140819231254/@comment-32390199-20141019200204

They can also pull a Naruto and just revive all the deceased villains xD. or just that one villain travels through time to collect Storybrooke's greatest villains to form an almighty army.

Cora, Peter Pan, Zelena and possibly Snow Queen. But that would be a huuuge stretch.