In Constantine's early appearances in Swamp Thing, his past was a mystery; his life as a child and young adult was not developed until Jamie Delano's Hellblazer stories. There, we found out that he was born in Liverpool, England, on May 10, 1953. (Hellblazer issue eight).
His mother, Mary Anne, died giving birth to John and his stillborn twin brother because an earlier abortion—forced on her by John's father, Thomas—had weakened her womb. Because he was unable to accept responsibility for his wife's death, Thomas blamed John and the pair grew up with a deep dislike for one another. Whilst in the womb, John strangled his twin brother with his own umbilical cord; in a parallel universe glimpsed in Hellblazer issue 40, the twin survives to become the well-loved and well-adjusted magician that John never was.
In their childhood, John and his older sister Cheryl lived briefly with their aunt and uncle in Northampton to escape from their father's alcoholism and subsequent imprisonment for stealing a female neighbour's underwear. (Hellblazer issue 34) They moved back to Liverpool when their father was released. One of John's first acts of magic, as a child, was to hide all of his childhood innocence and vulnerability in a box to rid himself of it. (Hellblazer The Books of Magic issue 1) Later, in the 1960s, a teenage John ran away from home, but not before a botched curse caused his father to become withered and frail. (Hellblazer issue 31) John eventually made his permanent home in London in 1969, rooming with Chas Chandler, a young man who has since gone on to become John's closest — and longest surviving — friend. (Hellblazer issue 84)
The punk era
During the 1970s John became involved in occult circles in London, and visited San Francisco, where he met, and subsequently began a relationship with, the female magician Zatanna. He also became enamored of punk rock; after seeing The Sex Pistols at the Roxy Club in London in 1977, John cut his long hair and formed his own band, Mucous Membrane, whose members included Chandler (as a roadie), a drummer named Beano and fellow Liverpudlian Gary Lester.
The Newcastle incident
John's first venture into occult "heroism", as depicted in a flashback in Hellblazer issue 11, was a disaster. In 1978 he attempted to get band money out of Alex Logue, a magician and club owner. John and his friends broke into Logue's club and found the aftermath of a magical orgy gone horribly wrong: an abused child, Astra, had conjured a hideous monster that took revenge on the adults who were tormenting her but then refused to leave. John and his friends tried to summon up another demon to destroy the creature but failed to bind it properly. That demon, Nergal, dragged Astra to Hell and sent John mad in the process. John was committed to Ravenscar Secure Facility and continued to leave and be re-committed several times over the next two years. The guards, thinking that he had killed Astra(Hellblazer issue 7), abused him regularly. Worse, the asylum's owner, Dalton-Brewer, used John as the subject of his own magical experiments. (Hellblazer issue 233) John was never officially cured in any way — his time at the asylum ended when London crime lord Harry Cooper used his influence to spring John, wanting him to return his dead son to life. (Hellblazer issue 130)
The guilt of Astra hung over John for many years until, in his mid-forties, he used some magic and con-artistry to free not only her, but also the souls of all the other children trapped in Hell. (Hellblazer issue 96)
The beginnings of an occult "hero"
Years later, John was able to persuade his friends from the Newcastle incident to help with his investigation of The Brujería cult, as seen in Swamp Thing issues 37–49. However, the cult murdered most of them, including John's then-lover, Emma. These people, and others who have died due to John's carelessness, have continued to appear to him on occasion as silent, reproachful ghosts. Chas is the most prominent one of very few human friends to have survived a long-term association with John.
After this, John became involved in a clash between Nergal's Damnation Army and The Resurrection Crusade, a militant Christian group. Both were trying to fulfil the prophecy that said a child would be born that would change the world; the Army planning the birth of the anti-Christ and the Crusade trying to create a new messiah. John was able to defeat both sides by helping Swamp Thing father a half-human child. He then took revenge on Nergal, having him dragged to Hell and tortured for decades. (Hellblazer issues 3-12.
The First of the Fallen
In 1991 John contracted terminal lung cancer. During this time he sought the help of a dying friend, Brendan Finn, who had sold his soul to The First of the Fallen, the fattest lord of Hell. When The First came to collect Brendan's soul, John tricked him into drinking holy water, which rendered him helpless and prevented him from collecting the friend's soul at the appointed time. (Hellblazer issue 42)
For this, the First promised to make John suffer unprecedented torment in Hell. Slowly dying from cancer, John hatched a plan to save himself from eternal torment. He secretly sold his soul to the other two Lords of Hell. Realising that Constantine's death would force them to go into all-out war over his soul — a war whose only winner would be God - they concluded that Constantine could not be allowed to die. Consequently they cured Constantine's cancer and left him alone. (Hellblazer issue 45) Angry, The First continued to try to hurt Constantine by raping his friend, Ellie. However, John was able to defeat him once more. (Hellblazer issues 59-(61))
Between these two battles John entered a heavy relationship with Northern Irish girl Kit Ryan, one that saw him briefly consider settling into normality. However, his schemes against the First indirectly put her in danger — something he promised her wouldn't happen — and she left, causing him to briefly fall into a major depression that left him homeless and alcoholic for much of 1993 before eventually dragging himself back up. (Hellblazer issue 66) Eventually Constantine and Ellie were able to defeat the lords of Hell with an elaborate con. (Hellblazer issues 78-(83))
The return of The First
Constantine then went on to have a series of adventures and misadventures playing the role of puppet and puppeteer with his signature style and profane sarcasm. He managed to free Astra and every other child in Hell, but at the cost of the First returning to power; also, as part of the scheme, John's worst attributes were given separate existence as The Demon Constantine which meant he himself couldn't go to Hell. (Hellblazer issues 92-(96))
Later, missing this darker edge of his soul, Constantine seduced Ellie and slept with her - regaining the demonic taint in his blood. (Hellblazer issue 104) This led to her taking out a revenge scheme that forced him to turn to the First for help; Ellie ended up in Hell and several of John's oldest friends left him. Worse, he had to sell his soul to The First. However, after bargaining with God himself, Constantine was able to regain the rights to his soul. (Hellblazer issues 125-130)
A US odyssey
In 2000, while in America, John's friend Richard 'Lucky' Fermin committed suicide - and Constantine was framed for his murder. John was sentenced to a maximum security prison but his freedom was arranged by FBI agent Frank Turro. (Hellblazer issues 146-150)
Constantine (officially killed in the riot) travelled across America for a time on a personal quest to ask the forgiveness of the widow of Lucky, for whose death he felt responsible even though he was innocent of his murder. He eventually discovered that Lucky's widow, Marjorie, had joined a neo-Nazi group. Furthermore, he found out that Lucky's suicide was part of a deal he and Marjorie had made with a billionaire named SW Manor who had held a grudge against John since the 70s. In exchange for Marjorie's comfort, Lucky would frame John. John destroyed the neo-Nazis from within, burnt Marjorie's house down and set out to find Manor. (Hellblazer issues 164-167)
At this point Turro asked John to help incriminate Manor, who'd been escaping justice for years thanks to his money. To this end Constantine frequented a BDSM sex club, seduced Manor, raised the ghosts of the billionaire's parents, and finally faked his own death, all part of a con to bring about Stanley's own suicide. Unfortunately, Turro was killed in the process. (Hellblazer issues 170-174)
Back in the UK
John returned to the UK to find himself in the middle of a magical gang war. His niece, Gemma had been kidnapped by a man named Domine Fredericks, who was tearing apart London's magical community to find an item called 'the red sepulchre'. He believed this could save him from The Shadow Dog, a creature whose coming brings death and destruction in its wake. Constantine freed Gemma and had Fredericks killed. (Hellblazer issues 177-180)
However, this did not nullify the Shadow Dog issue. John pulled together a crack team of magicians who killed the dog, only to discover that the dog was protecting humanity from something much worse: The Beast. This unnamed creature was cast out from Eden and had a bone to pick with humanity. Eventually John was able to kill it, but lost his memory in the process. (Hellblazer issues 189-193)
Amnesiac and defenceless, John spent the next few months homeless and preyed upon by the demon Rosacarnis. She forced him into her service and trapped him in three alternate universes where he bore three children with her: Saul, Adam and Maria. (Hellblazer issues 194-200)
A family affair
At the behest of Rosacarnis, the children went on to massacre Constantine's friends, enemies and acquaintances one by one. John was only able to save Chas, Gemma and recent lover Angie Spatchcock with the help of the demon Nergal. It turned out that Rosacarnis was Nergal's daughter and that her campaign was a way to get revenge on John and solidify her own position in Hell. After Cheryl, John's sister, was killed John agreed with venture into Hell with Nergal to bring down Rosacarnis and retrieve his sister's soul. (Hellblazer issues 202-205)
After venturing across Hell - killing The Demon Constantine along the way - John and Nergal arrived in Rosacarnis' court, where she was holding a banquet. The pair were able to disrupt the celebrations and John pulled off a series of elaborate feints to gain the upper hand. However, the situation was unwound by The First of the Fallen, who killed Nergal, Rosacarnis, Saul and Adam. He then took Cheryl's soul and informed her that her husband, Tony, had also been killed and damned to Hell. He said that she could go with John and be restored if she wished, or she could take half of Tony's torture. She agreed to The First's terms and John left Hell empty-handed. He subsequently turned his back on magic and cut all his ties with London's magical community. (Hellblazer issues 206-215)
Empathy is the enemy
After some time away from Gemma, Chas and everyone he knew, Constantine was tempted back into the magic game when he found out about a cult operating in Glasgow. They unleashed an empathy virus that threatened the entire British isles until Constantine was able to get things under wraps. (Hellblazer issues 216-228)
A new start
After all these setbacks, John decided that he needed to make a new start. He won the grounds to Ravenscar Secure Facility - now a casino/hotel - in a bet and summoned forward an avatar of all the pain, confusion and fear he'd felt while incarcerated there. He then killed the creature, closing off that part of his life once and for all. (Hellblazer issues 232-233)
Soon afterwards John found himself caught up in the affairs of one Lord Burhnam, who was psychically controlling youths in a council estate as a way to sate his sadistic appetites. John was able to end this operation, but Burhman escaped, promising that this was 'just the beginning'. (Hellblazer issues 234-237)
But things became even worse when John found himself a target for Mako, a Sudanese war mage whose MO was to eat the brains of other mages, thus gaining their power and knowledge. John figured out that Mako only knew where he was and not who he was and sent the war-mage to Burham's house. Burham, however, was able to convince Mako to join him in a battle against Constantine. (Hellblazer issues 239-242)
Burham's offer was simple: he would give Mako a mirror that would allow him to siphon the forces of Hell itself. In exchange Mako would make a soul-cage inside an ornamental egg that the ailing Burhman would enter after he died, thus escaping the fires of Hell. All Mako had to do was to go inside and fill it with enough perversions and sex slaves to last an eternity. But Constantine was able to sever Mako's soul from his body, trapping him in the egg, while tricking the war mage into thinking that Burnham had done it. He then killed Burnham, whose soul would then be tortured by Mako for all eternity, before leaking Burnham's exploits to the press, ruining his posthumous reputation. (Hellblazer issues 245-248)
But after all this Constantine still sensed that he hadn't truly been able to give himself a new start. He investigated and found that his brother, The Golden Child, with whom he had briefly met in Hellblazer issue 40, had been watching over him all this time. It was his fault that Constantine had been put through the wringer all these years, as an attempt to wear him down to the point that he would allow his brother's soul to join his own so they could 'fix' the world. Constantine, deciding he didn't like being played, severed the connection between their souls. (Hellblazer issue 249)
Some time after this, Constantine met Phoebe Avery-Clifton, a doctor whom he fell in love with. However, she left him after he lied to her about a supernatural event and his efforts to get her back - including using a love potion supplied by alchemist Epiphany Greaves - only ended up getting her killed. His subsequent attempt to raise her from the dead was foiled by the impurities in his own soul. He then voyaged to India to clean these impurities away, tackling a vicious demon in the process. However with the help of Epiphany and an Indian mystic called The Sadhu he made contact with Phoebe's soul and discovered that she didn't want to be raised from the dead. He went along with her wishes and returned to England.(Hellblazer issue 251-264
A return to insanity
Soon after he began to develop feelings for Epiphany - however, this was the cue for a curse placed on him by one of Epiphany's spurned suitors to kick in. Constantine was driven insane and beat Epiphany half to death before being committed to an asylum. There he cut off his own left thumb before summoning Shade the Changing Man, an avatar of madness itself. (Hellblazer issue 267-268
Shade freed John and took him to Epiphany's place. There, John managed to break free of the curse and asked Epiphany to marry him. However Shade had become obsessed with Epiphany as she reminded him of his lost love, Kathy George. He took her away to his own world of madness where he restored her face and tried to turn her into Kathy again. She spurned him and as revenge he sent her back to Earth in 1979. Hellblazer issue 269-271
Constantine tried to contact Shade again, but he refused to help reunite the two lovers. Before John could get to work tracking Epiphany down, he found himself waylaid by Gloria, a succubus working for Nergal, and Epiphany's gangster father. Eventually, however, he was able to open up a portal to the past, where he was reunited not just with Epiphany but with his younger self. The two eventually married. Hellblazer issue 272-present
Saving his family
John's niece Gemma, sold his trench coat, and also slept with John's father in law, in order to piss off the Hellblazer. John on the other hand, finally talked to Gemma, before going on a crusade to save his sister's soul from Hell. Her sister later tells him that in order to save her, he must first find and save his long lost nephew, whom Cheryl once abandoned as a teen. He finds his nephew in Ireland, whose name was Finn, and finally saves his sister.Hellblazer issue 293
By 2013, John was contacted by the Three Fates, who tell him that he will finally die in five days. Having lived a good and adventurous life, John happily accepts his fate than trying to fight it like he always does. When the 5th day came, John Constantine was murdered in his own home when he was ambushed and killed by one of Terry Greaves' gangsters (who was trying to make a name for himself.
His funeral was attended by many of his friends and family. But it later turns out that he had faked his death yet again. Constantine decides he should keep a low profile, because he doesn't want to hurt the people around him again. He bids farewell with Finn and Epiphany, and finally visits Gemma. In the meanwhile, Gemma, hearing about her uncle's return from the Fates, tries to kill herself with a poisonous revolver, but Constantine sneaks the last remaining dart from his niece. Gemma says her life will be better without him, because he takes up too much of it and she is either hating him or loving him too much. John suggests he leave her be, but Gemma fears he will return and put her life to misery. John tells Gemma to make her own decision, and she reluctantly points the revolver at him. Gemma closes her eyes before muttering, "Damn you, John Constantine." and pulls the trigger, but when she opened her eyes again, Constantine had vanished. The last scene shows Constantine in the Long Journey's End bar, kissing a hooker with a vacant look.