He is mentioned by the three fates who said Constantine had traded Morpheus' bag of sand to a demon. Morpheus tracks him down in the human world, arriving in London in a grand cloak which Constantine said would be "dead embarrassing" to be see with on public transport. He assists in Dream's pursuit of the bag of magical sand, a pursuit that ends with the death of an old girlfriend, and in return, Morpheus cures him of the nightmares he's been having.
Constantine is not seen again until issue 71 of Sandman. In Sandman Presents: Love Street, we see a young John Constantine in the house of Morpheus when Dream was still being held captive.
He is descended from Lady Johanna Constantine who also had dealings with the Endless.
John is known for his endless cynicism, deadpan snarking, ruthless cunning, and constant chain smoking, but is also a passionate humanist, driven by a heartfelt desire to do some good in his life.
John Constantine is an occult detective and professional sorcerer from Liverpool, but currently lives in London. He is a cynical, foul-mouthed, chain-smoking, anti-hero. He appeared in his own series, Hellblazer, for many years during which he aged in real time. He has been a member of Justice League Dark, the Newcastle Crew, and the Trench Coat Brigade.
He has also acted as a supernatural adviser and ally to the Swamp Thing appearing in Saga of the Swamp Thing #25.