WARNING: The following contains major spoilers for Justice League Dark #17 by James Tynion IV, John Kalisz, Javi Fernandez and Rob Leigh, on sale now.
Justice League Dark continues to redefine the DC Universe's magical realm after effectively making Wonder Woman the face of mysticism. However, Diana of Themyscira is now possessed by Circe, resulting in dangerous times at her magical vault, where Injustice League Dark is now under attack.
But while her allies struggle against these enemies on Earth, Diana's soul has been locked in a dark realm alongside Witchfire, leaving her fighting to devise a plan to take back her body. As she formulates a strategy, though, DC's most terrifying villain, the Upside Down Man, makes his return.
The Upside Down Man was earlier revealed to be the dark half of magic, with the light half manifesting as Hecate after the act of creation. She locked him away, and schemed for eons to reclaim magic as he believed was stolen from him, and then seeded throughout the cosmos. The Upside Down Man used the Otherkind and Lords of Chaos to assault Earth and the corporeal realm in an attempt to steal back what his sister took, but he was once more sealed away in the dark dimension.
He feasted on Hecate, however, which by all rights should have satisfied him. Yet that meal only created more trouble: Hecate's fall permitted the witch Circe to absorb her power and become the avatar for her magic. All along, Circe was playing the Justice League Dark team against the Otherkind, because she didn't want to share magic with the Upside Down Man. Now, she's determined to make the evil god Eclipso, in his prison in the Black Diamond, even more powerful, and employs Floronic Man, Papa Midnite, Klarion and Solomon Grundy in the mission.
As that happens, the slithery Upside Down Man sneaks up on Diana and Witchfire, and warns them things can "always get worse," hinting he's preparing to devour their souls. Interestingly, Circe could have left the two as bait for the Upside Down Man so they could form a potential alliance, but seeing as she has the power he wants, it's unlikely. The Upside Down Man could bargain with Diana to become a temporary ally against Circe. He might even have a damaged Hecate there with him so Wonder Woman may have access to both siblings to retrieve what Circe stole.
It will be a deadly alliance, and one Diana can't trust. However, at this point, she has no choice. The Upside Down Man doesn't like Circe, whom he undoubtedly views as merely another Hecate -- a meal he's owed. It's unclear whether has more of the Otherkind, so we're left to wait to see what his discussion be like with Wonder Woman. The Upside Down Man can also bring back the Lords of Chaos -- or at least a new iteration -- so no matter which side he's on, he's a true monster. He's a creature steeped in deceit and death, after all.
Justice League Dark #18 goes on sale Jan. 1, 2020.