John Constantine
So, first we'll have some basics. Then we'll get to the ideas that I'm toying with given they could possibly need mod approval?
1. John is now 52! 2. He has lung cancer, because he's canonly doomed to have it. Everyone who pointed out his smoking habits can laugh at the irony. 3. Following Hellblazer canon, how about he somehow managed to get the scar he acquires. 4. Also, following Hellblazer canon for the kick of it, John has lost his thumb (a little graphic so watch out) along the way. Probably, like in the comics, trying to summon some entity. Maybe even did a spell against the Wardens and it horribly backfired? It's a mystery~ 5. (if Zed mun approves!) He probably had a relationship with Zed that was deep, meaningful, and he shot himself in the foot and ruined it. Most likely he used her powers to benefit himself in some fashion as opposed to really helping her.
Ideas Needing Mod Approval? - As I'm literally just pulling from comic canon, he does have demon blood in him that makes him age as slow as a sponge moves across the ocean floor. I'm not sure how it could happen or if it should/can - hence this section! - Twenty years gives you plenty of time to know about a possible underworld? Magic orientated, maybe just some dark creepy secrets. John canonly has contacts out the arse when it comes to this department, so it would be something he would have established. The thing is, who these people are/what he'd know would obviously need to work within the game/what is established.