This new promo includes new footage such as:
1. Emma training to FIGHT!
2.David shooting at "nasty, siren-like mermaids."
3. Emma commanding Regina to either help get "her" son back or to get out of the way.
The season 4 finale of Once Upon a Time left many a fans breathless as Emma Swan, the saviour, seemed to have become the embodiment of pure evil, "The Dark One".