The character John Constantine was originally created by Alan Moore, and first appeared in the horror series Swamp Thing. When he first appears, John Constantine is a trenchcoated sorceror with a tendency to get on people's nerves, and who also happens to be the spitting image of the musician Sting (in fact, Alan Moore once stated that he modeled the character's appearance after Sting, and in one Swamp Thing story this is acknowledged when Constantine is observed to be rowing a boat named The Honourable Gordon Sumner, Sting's real name).
The character was given his own comic book - Hellblazer - in 1988, which was initially written by Jamie Delano and illustrated by John Ridgeway, who had previously worked on the UK titles Doctor Who Monthly, Warrior and 2000 A.D. The front covers of the early issues usually featured striking semi-collage designs by artist Dave McKean. Others who have worked on the series include writer Garth Ennis and artists Mark Buckingham and Steve Dillon. Hellblazer is a decidedly dark comic book, its main character often seen doing morally questionable things while tricking his way through a modern world with a lot of magic and supernatural confict going on behind the scenes. While sometimes clearly heroic, Constantine is more often than not merely fighting for his survival and usually making more enemies in the process. He is also highly manipulative, and has frequently sacrificed the lives and souls of others around him in order to achieve his ends. Many of these individuals haunt him, and he frequently finds himself being followed around by an ever increasing entourage of ghostly figures.
Constantine has been featured in several other comic book titles, such as The Sandman and The Books of Magic. A Hellblazer movie entitled Constantine is scheduled for the end of 2004, and will likely feature Keanu Reeves as John Constantine.