Constantine was originally a film adapted from the DC Comic HellBlazer has plot elements from the story arc of Dangerous Habits and the Original Sins ,is a fantasy action horror drama starring Keanu Reeves in the lead and directed by Francis Lawrence.
The character John Constantine first appeared in The Saga of Swamp Thing.The character was developed by Alan Moore,John Totleben,Rick Veitch and Steve Bissette.
Constantine further got developed into a Television series by Daniel Cerone and David S. Goyer. The series stars Matt Ryan in the lead as John Constantine who is a British Exorcist and detective who hunts supernatural creatures and entities. It also stars Lucy Griffins,Charles Hafford,Angelica Celaya and Harold Perrineau.
John is a demon hunter and a master at exorcism and occult.He struggles with his past because of his sins while protecting innocent people from evil supernatural entities
The first season aired on NBC in October 2014 till February 2015 but the show got cancelled by NBC because of low ratings.As the showed aired at 10pm it lost its core audience ,though the live audience was less there was a string number of audiences streaming the show.
Disappointed fans launched a campaign to save the show so did the Warne Brothers Studio but no network picked up the show after NBC announced the cancellation.
In 2018 the show got a revival when CW made an animated series with all episodes combined as a full length film.Moreover Matt Ryan also made an appearance In the film Legends of Tomorrow by Warner Bros. So there are chances of Constantine returning with a rand new season with Warner Bros.