Constantine & The Ghost King
One of my favorite tropes from the Danny Phantom x Dc crossover is Constantine's reaction whenever Amity or the Ghost Realm is mentioned by the Justice League/Batman is "Fuck no. I'm out." But what if he had a reason?
Constantine made a lot of deals with all types of beings. Some human, some not. So who's to say that he hasn't made a deal with a ghost in a time of his life?
So imagine around a time where he was really desperate that he made a deal of sometime with the Ghost King, or possibly the Ancients since they defeated him. And they agree to his deal in return that he will help the Ghost Zone when the time comes, and Constantine agrees because, well, he really doesn't have a choice at the matter.
So fast forward possibly years after Constantine saved the world and the deal with the ghosts just piled on to the ever growing list of deals he owes plenty of others and doesn't think about it.
Until, that is, he hears about Amity Park. The most haunted place in America that really is haunted. With ghosts that would no doubt alert the Ghost King if he stepped even an inch inside their perimeters.
So Amity Park was marked with a big DO NOT ENTER by Constantine and he added it to his ever growing list of places that he's never going to go with a ten foot pole.
That is, until there's a potential world ending threat that not even Justice League Dark could help with. So they really had no choice but to contact the Ghost Zone to get the Ghost King's help. Though Constantine did warn the others that the Ghost King isn't one that they all had to be careful.
So there they are all standing. The JL standing in apprehension of the so feared Ghost King, Constantine in fear of the summoning the king would enact the deal they made.
He's waiting. He's waiting. He's waiting. And.....that isn't the Ghost King he remembers.
No, the supposed king before him looks like a kid. A teen at best. But the toxic green eyes that scanned the room told him that this was more than just any teen.
One explanation later, they learned Pariah Dark was defeated and this kid was the new king and Constantine felt a small shimmer of hope.
If this was the new Ghost King, surely he'd be out of his deal, right? No Pariah Dark to tell him what to do and whatnot.
So with Phantom's help they managed to defeat the evil and Constantine was more than happy to finally get out of there and drink the memories away.
But fate reminded him of his life when Phantom was right in front of him, a knowing smile on his face.
"John Constantine. It is time that you completed your contract with the Ghost Zone."