...."exorcist, demonologist and master of the dark arts" (not to put on airs)....but, here's a little on the DC Comics history of the character that Matt Ryan looked like he stepped off the pages from...
....though, fair warning, this is not a tale for kids, as John demonstrates a knowledge of language that wouldn't make it into television, using his sarcastic wit to its fullest, including a few "f-bombs", and quite a bit of gory action...but all part of the regular character of John Constantine.
Zed returned briefly to John's life, as a pagan sorceress living in Scotland.
First of the Fallen
....dealing with the things no one wants to talk about with a British wit and smoking talent (though his smoking did cause him pain....).
John even showed up here and there in the regular DC Universe, putting in the occasional cameo in the Spectre, in Swamp Thing and Sandman, getting name checked during Underworld Unleashed, even in an issue of Challengers of the Unknown....
...originally meant to be part of a longer story, that story didn't happen, but the two-page cameo was kept, with John and Ollie meeting in a pub, John giving Green Arrow directions, and Ollie found a non-mystical solution in the next issue, ending this storyline all too quickly.
Both Green Arrow and John Constantine would find themselves adapted to television....