WARNING: The following article contains major spoilers for Justice League Dark#18, by James Tynion IV, John Kalisz, Javi Fernandez and Rob Leigh, on sale now.
Wonder Woman hasn't been the best judge of character in Justice League Dark recently, and not for a lack of trying. After seeing Doctor Fate turn on them, Diana of Themyscira, accepting her place in the universe as an avatar of magic, tried to partner with Circe, only for the witch to betray her.
It turns out Circe wanted all of Hecate's power for herself and with the light half of magic (from the spark of creation) imbued in her, Diana's enemy is now wreaking havoc using the Amazon's body at the Hall of Justice. To counteract this, Wonder Woman decides to make her deadliest alliance ever and it's one that could have dire repercussions moving forward.
Circe is using the Injustice League Dark to try to free the demonic Eclipso and garner other mystical relics the Justice League collected over the years. This is part of her becoming the magical powerhouse Hecate always wanted to be, but in Circe's case, she'll have all the cogs in place to truly surpass the queen of the witches. To her, becoming this ultimate magical avatar is a life goal and she's just a few steps away, however, she doesn't know Diana's spirit is speaking with the Upside Down Man.
This sinister villain tried to retake magic from Earth only to be repelled by Diana's powers early on in this title, and now he's the person she's brokering a deal with out of sheer desperation. He was the dark half of magic Hecate banished from reality. As he schemes with Diana, Upside Down Man vows to give her the power to retake her body once she can deliver on the promise she makes initially. As the Upside Down Man enjoys the irony of Hecate's power being used for mankind's downfall, Diana tells him if he helps her, she'll bring balance back by restoring him to reality to be the polar opposite he was meant to be.
In other words, she's offering him freedom and a way out his dark prison. The Upside Down Man entertains the idea and agrees to work with Diana because it's going to be fun watching her as his champion, but also because even if she loses, Earth will be destroyed by Circe and remade into something more warped. It's a win-win, as he's enjoying life in this dimension but he does see the benefits to being released and fighting whoever represents the light out there.
He powers Diana up to reassume her form, but as part of the bargain, he has an insurance chip thanks to Witchfire, whom he bites. The ghost is bitten in vampire-like style, and it appears he marks her to ensure Diana doesn't betray him. Time's running out. With Wonder Woman against the clock, she now has to hustle to get the job done to save her friend.
In other words, the Upside Down Man is in control of the main chess pieces, puppeteering Diana in a way she never thought possible. As his vessel, she does want to restore magical balance, but she knows she has to pick the lesser of two evils to achieve this goal. Both villains want to devour the world, so it's all about who's the bigger monster, and at this point, it's Circe. Still, the Upside Down Man can't be trusted, and unless Wonder Woman has an ace up her sleeve, she may have irreparably doomed mankind by partnering with him, thinking it's the best move for the universe.
Justice League Dark #19 goes on sale January 29.