Doctor Fate's History
Anti-Life Infection
Not long after the infected Anti-Life Equation began turning people into the Anti-Living John already found himself running for his life from a massive horde. After ducking into a cab he immediately told his friend Chas to get them out of there, unfortunately, Chas had already been infected and John was forced to burn him to ashes. Constantine tries to drive out of there but he doesn't get far, immediately crashing the cab into the back of another. Thankfully he's saved by Mister Terrific and a small group of other heroes. They ask him for his help, but John declines saying he's tried already and decides to get drunk at the Oblivion Bar instead.
John's conscience gets the better of him and decides to help them anyway. He headbutts Waverider, and elects to buy the remaining heroes time to go back in time but is attacked by an infected Big Barda who immediately rips Terrific in half. In the end John's the only one left as Blue Beetle gets infected and Booster Gold ceases to exist.
After getting Waverider killed John is once again saved, this time by Zatanna and Doctor Fate. He calls the two out for arriving too late to save the others and swears that world isn't over yet until he says it is.
The Unkillables
Sometime after John would set up shop in the Gotham Jungle with Zatanna and Nelson, turning it into a sanctuary from the infected. When the Unkillables fight their way through the hordes of Anti-Living and the infected Wonder Woman they welcome them in with open arms.
Dead Planet
Five years later, Constantine would come down with survivors guilt over failing to save the other heroes and spends his time drinking in abandoned bars, usually with only a box full of Chas's ashes for company. When he's not getting drunk he's usually with the Shadowpact, Jason, and Rose, saving anyone that they can find. After Zatanna takes out an infected Fire they are confronted by Swamp Thing who needs their help to investigate another save haven in Austraila.
They arrive, and it appears to be surrounded by a moat of blood and hellfire, unfortunately they realize too late that it's actually an infected Plastic Man. The massive monster kills Blue Devil, Ragman, and almost Zatanna by filling her lungs while Constantine and Detective Chimp fall into Plastic Man's maw.
After being saved by Swamp Thing, Zatanna forces O'Brian into the fire. They then investigate the bunker and find that it's inhabited by Penguin, Maxwell Lord, Jason Blood and many of the wealthy that were left behind on Earth.
Jason transforms into Etrigan and warns Constantine of Trigon's coming and his plans to wipe out the entire planet. Just then they're interrupted by Swamp Thing's rampage, revealing that the people within the bunker had captured Floronic Man and forced him to produce food for them. After Swamp Thing kills Maxwell Lord, they are chased out by Dr. Ivo's AMAZO army.
John returns to the Gotham Jungle and plans with the others to awaken the cure within Cyborg. After tracking down Mister Miracle, who survived, John and Bobo convinced Scott to help them find Metron and get the Mobius Chair from him. This attempt succeeds through lending Metron Madame Xanadu's crystal ball in return for a seat in the Mobius Chair.
Later, John decides he needs to become much stronger to defeat Trigon. Getting assistance from the Bat Family, Swamp Thing, and Etrigan, John goes on his journey to stop Trigon. First they stop in Nanda Parbat, where he takes the Spear of Destiny from Rama Kushna and absorbs Deadman into Ragman's cloak. Next the group goes to the Rock of Eternity to obtain the Staff of Shazam. Cassandra obtains the power of Shazam and gives the Staff to Constantine, but they lose Jason to Captain Marvel Jr.
They then return to the Gotham Jungle, where Constantine stores the magical weapons in the Tower of Fate. Both Zatanna and the Phantom Stranger try to stop him but John insists it's the only way. Meanwhile, Trigon arrives.
Doctor Fate is called by John, who is donning the mystic artifacts he's collected. John requests the doctor's helmet and amulet. The Phantom Stranger steps forward and stabbed Nelson with the Spear of Destiny, stating that John had showed him the future. Constantine obtains the helmet by grabbing the Staff of Shazam in one hand and the helmet in the other, and shouting the magic word. Lightning strikes, and the helmet is removed.
While Zatanna and the Phantom Stranger stall Trigon, John goes to the sanctuary in Australia, where he absorbs the inhabitants' souls with Ragman's cloak, empowering him even more. He then goes to battle the demon. Angrily, Trigon slams John Constantine into the ground, killing him. But this was planned, as John rises as a ghost due to him taking Deadman's power earlier. John then goes to possess Trigon, succeeding, and then stabbing himself with the Spear of Destiny, erasing both Trigon and himself and saving the world.
