We've seen the Storybrooke gang face evil, fall in love, succumb to darkness and battle dragons. But on the 100th episode of Once Upon A Time, they will face something even stranger: we'll see Emma Swan, along with her friends and family, go to the depths of Hades to search for her beloved Captain Hook.

It's not every day that shows reach the 100-episode mark, so ABC plans on making this episode special. That's not an easy task, considering that the show has always brought a special kind of magic and joy to the world of fairy tales, so the network upped the ante by sending the team to the Underworld.

However, there's more: not only will we see Emma and company adventuring their way through Hades, but we will also go back in time as each character deals with something from their past.

Here's what to expect during Once Upon A Time's 100th episode.

Welcome To Hades

The 100th episode of Once Upon A Time takes our team of heroes - and occasional villains - to the realm of Hades, the Underworld, a place where the dead go when they haven't quite yet said goodbye to the mortal world. Hades also looks a lot like a twisted version of Storybrooke, but more post-apocalyptic and considerably more frightening. This version of Hades also features more mythological aspects taken from its Greek counterpart, such as the River Styx.

"There's a reason for why some of the Underworld appears the way it does, why it appears to be a Storybrooke in a different form," co-creator Adam Horowitz said to TV Line. "Without us spoiling too much, there's a very specific reason why the Underworld appears as a screwed-up version of Storybrooke."

So what is that reason? Well, let's assume that it's to give our heroes a false sense of familiarity, so that they become even more shaken as events unfold in a disturbing fashion that are very unlike anything that happens in the mortal version of Storybrooke.

The Dead Come Back To Life

What's dead always comes back, at least on television. But Once Upon A Time decided to not actually bring the dead back to life, but, instead, decided to keep them where it is that the dead go, at least those with unfinished business. This is where Hades comes in. And this choice gives the show a chance to revisit some of the series' most interesting characters from previous seasons.

So which dead characters will we see again? So far the list includes Cora, Peter Pan, Neal, Sidney Glass, The Blind Witch and Prince Henry. And what do these characters have in common? Since they are in Hades, they have unresolved issues, and it's likely that this will involve Emma and the others.

"We're exploring the idea of unfinished business - things that were left unsaid, left undone, things in our past we wish we could correct, things in our past we wish we could go back and do," creator Edward Kitsis said to Yahoo. "I think a lot of these characters have a past that haunts them and prevents them from moving forward."

One thing is for certain: have the tissues ready for the reunion between Emma and Neal. There are also the scenes between Regina and her mother, Cora, to look forward to: those two definitely still have a lot to say to each other.

There's A New Bad Guy To Conquer

The citizens of Storybrooke have faced a lot of villains over the show's history, including crazy snow queens, wicked witches and even evil versions of themselves. However, we'll meet the new bad guy in town in the 100th episode, who is probably the nastiest of them all: Hades.

Although Hades isn't being played by James Woods, as in the Disney film Hercules, it looks like actor Greg Germann will still look the part, complete with fiery blue hair.

"Hades is such a fun, endlessly creative challenge," Germann said to Entertainment Weekly. "Anything goes. The creators bring him to life on the page with the same out-of-the-box unpredictability that they bring to the rest of the show. They strike the perfect balance between keeping things grounded and letting things fly - sometimes literally."

It's likely that the heroic Storybrookers will have to go up against Hades during their search for Hook, because it's also likely that Hades doesn't like the idea of having his denizens taken away from him.

Saving Hook Won't Come Easily

Although Emma and the others are in Hades to save Captain Hook from death, it seems that he may not actually want them to do so. Hook understood what he was doing when he sacrificed himself to save Storybrooke. He became a hero by saving the lives of Emma and the others.

Not only that, but the group will face multiple obstacles in Hades in their quest to find Hook in the first place. There will be mental as well as physical obstacles, because being in the Underworld means that they will have to face themselves, holding up a mirror to their own flaws and unfinished business.

"There are obstacles everywhere," Sean Maguire, who plays Robin Hood, said. "There are a lot of bad people from the past coming back, and they're not too happy with our heroes. If Once Upon a Time was the Star Wars franchise, this would be Empire Strikes Back. This is gonna get dark, it's gonna get a little scary, and there are going to be a few surprises."

The 100th episode of Once Upon A Time airs at 8 p.m. EST Sunday, March 6, on ABC. Here's to 100 more, especially now that the series just got picked up for a sixth season.

Photos: ABC