The Justice League Dark is a group of some of the most unknown and dark super- and antiheroes from DC/Vertigo, who deal with equally dark villains and situations. The team had its first comic series run with the New 52 in 2011 made of 40 issues. The first members of the team were: Madame Xanadu, John Constantine, Shade The Changing Man, Zatanna, and Deadman. Different characters were added and removed from the team within every issue (Black Orchid, Frankenstein etc.), but probably the most fundamental members are: John Constantine, Zatanna, Deadman, Swamp Thing, and of course Madame Xanadu who brought the team together herself in JLD #1.
John Constantine has always been an exorcist, but with the New 52 he become a magician: despite his many flaws – such as arrogance and selfishness – he does have a heart and his abilities turn out to be quite useful when it comes to defeating evil.
Zatanna is a very powerful magician and even became the leader of the Justice League Dark in issue #30. She has been romantically involved with Constantine, but given his selfish and cold behavior, their relationship didn't last.
Swamp Thing is considered to be the great representation of the Green itself. He therefore has an incredible control over nature which makes him extremely powerful. He first assisted the team in issue #19.
Madame Xanadu is a mystic and fortune teller of great power. She has lived through centuries, gaining more power as she acquires more experience. She brought the team together in issue #1 when she saw a threat coming for humanity.
Deadman is the ghost of an acrobat who was assassinated during a performance. He can possess people's bodies, taking full control over them.
In 2017 an animated movie produced by Christopher D. Lozinski and directed by Jay Oliva came out. The movie starts by a first taste of the threat they're going to have to face. Batman and the Justice League think of who might be appropriate to deal with such magic problems, and he is led to Constantine and eventually all the members get recruited to save the situation. Constantine, Deadman, Zatanna, Swamp Thing and Etrigan the Demon who shares Jason Blood's body are the main members of the team, but we get to see Black Orchid as well (in the house of mystery). The plot and storyline were good and interesting, and the script perfectly reflected the characters’ personalities and relationships. For example, Constantine’s typical rude sentences and his conversations with Zatanna as well as Deadman's somewhat ironically lively presence, compared to the others – he's the one most likely to give a humorous comment on occasion. The only real problem is that Batman didn't need to be a main character. It would've been more accurate to have Madame Xanadu bringing the team together like in the comics.
In 2012 there were rumours about Guillermo del Toro working on a Justice League Dark live action movie. Later in 2013, Del Toro confirmed that he was working on a film titled “Dark Universe” and that it was meant to center around Constantine recruiting the other members.
He confirmed that the production would begin after ending “Crimson Peak”, but he couldn't go on with the production without Warner Bros’ approval.
In 2014 del Toro stated the film would be independent from the DC Extended Universe and in november del Toro’s script was complete and handed in to Warner Bros.
In 2016 it was announced that del Toro, Scott Rudin, and Michael Gilio were working on the film, and at the San Diego Comic-Con in July 2017, the film's title was announced to be Justice League Dark which confirms the movie's existence in the DCEU project
The team totally deserves a movie. Moreover it would be good for the DCEU, given their popularity with comic fans. Also since the DCEU seems to be in a rush to bring all of DC’s main heroes on the big screen, the Justice League Dark is the best choice to bring in a new, “stranger” side of this continuity. Adding the “magic world” into this extended universe is an innovation that might attract new people and that might make the waiting fans happy. Perhaps, if the movie does well enough, DC might give the team a new comic run.
The New 52 series gave many ideas of who the villains might be (probably not Enchantress, since she has already had her role in Suicide Squad). It is, maybe, slightly more difficult to decide who the definitive main members should be, since there was a variety of members in the comic series.
But there's hope. The comics offer a huge number of different ideas, different plots, and different villains.
And obviously there is nothing more exciting than seeing our favorite heroes on the big screen!