Ladyawesome45321: I wrote this after that episode aired, but I've been toying with the idea of Zari possibly sucking the air out of lungs for a long time and seeing the show confirm that Zari could actually do that if she wanted to... the show went dark for a moment, and I loved it. Thanks for reviewing and happy new year!
Demon
The demon had been stuck inside his body for two months.
To the human mind, two months was like an eternity. John couldn't even remember under which circumstances he allowed the demon to enter his body, or which demon it was, but it had made itself at home and it pushed down John's consciousness. Of course, John wasn't one to back down from a fight, especially when it came to controlling his body.
Slowly, over the weeks, his attempts to break free became more futile. The demon was too strong as it paraded around in John's body. Constantine was fully aware of what his body was made to do and could only try to make sure he wasn't intentionally hurting people, even if he couldn't do anything.
The last straw came when the Legends showed up to fight the demon. They had contacted Papa Midnite and called other prominent people in the magic field, and those willing to banish the demon - not necessarily to help Constantine - had come to the battlefield.
When the demon laid its eyes on Zed and Chas, that's when John finally regained his will to fight back. The demon was powerful, and John did not want it to kill the only people he would ever consider calling "friends". He was so caught up in the struggle for control, he barely noticed how the demon fought the Legends.
At long last, John was free and the demon was gone. He fell to his knees, took a deep breath and panted. Getting rid of the demon had been exhausting.
Then he opened his eyes and saw the horror before him. The battlefield was literally burning, a big city in the distance. The demon's victims were either cut down clean or mauled beyond recognition. None of the Legends' guests survived, not even Zed.
John laughed maniacally. Usually, the minds of possessed people rarely survived for longer than a week, hysteria and insanity settling in on the second day. John made it out after two months, and that left his mind scarred. It had done more damage than he imagined, and he'd been too preoccupied trying to get out to notice this change.
Chas, having been revived, stood up from the battlefield and approached his friend, still wary of the demon that had been inside of him. "Is that you?" he had asked and John nodded.
"Yes, it's me." Constantine stood up and he kept his eyes on Chas. As soon as he came within reach, John snapped his former best friend's neck and walked off. Chas would be back. Or not. How many lives had he already used up? Oh, doesn't matter, there were bigger things to worry about.
In his insanity, he created the perfect demon paradise out of the United States, and those who opposed him were doomed from the start. Team Flash was dead within seconds, and Star City was completely wiped off of the map. In his conquest, he summoned demons and let them loose. They helped with the destruction, and Constantine led a small army to destroy the bigger cities of the country. Nobody on Earth could stop him.
The angels eventually did intervene, but by then it was already too late. The United States were left scorched and the few demons that made it beyond the border were plunging other continents into chaos. John managed to kill several angels, including Manny, before they killed him.
Constantine was dragged into Hell and there, he was welcomed with open arms. He was not planning to give up, however. Through hard work, intimidation and occasional incineration, he became a General of Hell. All demons listened to him as he commanded them to continue their destructive work on Earth.
During his eternity in Hell, he only saw Astra once. he walked straight past her like she did not matter anymore. She cried out his name and begged for him to save her. But he did not look back, and a cruel smile curled upon his lips.