Once Upon A Time might have seen some issues resolved in its midseason finale, but that doesn't mean that the season is over; in fact, in a new promo released by ABC, the citizens of Storybrooke must face something possibly even more terrifying than the Dark One.

In this new promo teasing the second half of season five, Storybrooke is now the Underworld and the souls of those who died in previous seasons are back to haunt the living.

Here's the official synopsis for "Souls of the Departed":

"The quest to find Hook begins as the town of Storybrooke becomes the underworld - where everyone you thought was dead and buried is alive and kicking!"

Please note that the following contains spoilers.

The promo teases characters who previously died on the series returning to life as the citizens of Storybrooke traverse the Underworld to help Emma (Jennifer Morrison) find Killian (Colin O'Donoghue), who died after the events of the midseason finale.

Some of the characters seen in the clip include Cruella de Vil (Victoria Smurfit) and Peter Pan (Robbie Kay), as well as Regina's (Lana Parrilla) parents (Tony Perez and Barbara Hershey). "There are forces here beyond your understanding," says Regina's mother.

Although events of the midseason finale were tragic, there's good news: Emma's back to being herself.

"She's back to savior magic," said Morrison to Mashable. "Her savior magic is intact. There is a mention that in the initial arrival in the underworld, anyone who's dealing with magic is shaken a little bit, but Emma sinks into hers pretty quick. So she's back into true savior Emma form in terms of magic pretty quickly."

The next episode of Once Upon A Time is special, not just for its story, but because it marks the 100th episode of the series. This is why many actors who played characters who died on the show will return.

"They were just interested in bringing certain characters back for the 100th," said Kay to IGN. "They really wanted to incorporate all of the faces, because they, kind of like Heroes, create this whole universe of characters, some of them loved, some of them hated—in good ways, though."

Once Upon A Time returns March 6 to ABC.