The following contains spoilers for The Joker #15, now on sale from DC Comics.
Most of DC's villains have found themselves absorbed into the overarching conflict at the heart of Dark Crisis, serving directly under Pariah's Dark Army or fighting as a member of Deathstroke's Secret Society. There are a small handful of holdouts -- but now, two of Batman's most iconic villains are back on the board and might be due for a Dark Crisis appearance.
The Joker #15 (by James Tynion IV, Giuseppe Camuncoli, Cam Smith, Lorenzo Ruggiero, Arif Prianto and Tom Napolitano) reveals that Joker and Bane are both back in the world and on the move. This means they could easily become major wildcards during a very tumultuous time for the DC Universe.
The Joker #15 largely resolves the former loose threads of James Gordon's hunt for the Joker around the world. The mission ultimately exposes numerous monstrous criminals, pushing them out of the shadows. Gordon explains the entire sordid affair to Batman, revealing his discovery that nefarious forces are cloning villains (leading to the creation of Bane's daughter, Vengeance) and uncovering criminal safe houses across the planet. Gordon also reveals that these discoveries nearly cost him his life -- while he was hard at work, Joker popped up and almost killed him. However, luckily for Gordon, and unluckily for Cressida Clark (a member of the Court of Owls), Joker ended up killing the latter instead before escaping.
The story concludes with Gordon returning to Gotham, still unsure of where Joker and Bane are. But he is content that at least some dangerous people have been brought to justice. Gordon is reasonably sure that Bane took his daughter back to Santa Prisca with him to plot their revenge on the people who created her to be used as a weapon. This is seemingly confirmed when a single panel shows that their attack is already set in motion. Meanwhile, the Joker evades capture once again and simply walks off into the sunset, with Gordon and Batman having no idea of where he's gone or when he'll return.
This means that two of the DC Universe's most terrifying villains are freely roaming the world, sight unseen. Under normal circumstances, this isn't ideal, let alone now with the Justice League supposedly dead. If Bane and Joker decide to make grand returns, it will most definitely wreak havoc on the Bat-Family, who are now without their leader. Considering Bane's last attack on Gotham resulted in him taking over the city and killing Alfred Pennyworth, any member of the family will be "fair game" for him.
To make matters even worse, with the Dark Crisis is now in full swing, Pariah has been recruiting people for his Dark Army, and he's proving to a great threat. He is so powerful that even Darkseid, an actual God, falls under his sway. There's little reason to think Pariah can't or won't recruit villains as invaluable as Bane and Joker. On the "bright" side, the two villains have a history of being uncontrollable which gives them an extreme advantage.
However, even if they don't get pulled in by Pariah, that doesn't in any way mean they won't cause chaos of their own. The Joker may rejoin the Legion of Doom (who've been confirmed to be back and monitoring the situation), helping elevate the villainous alliance during a time of vulnerability in the DC Universe. Joker and Bane's return comes at a time when things could take some seriously dark turns -- and it might only be a matter of time before they get involved in the Dark Crisis.