John Constantine's past is catching up with him on DC's Legends of Tomorrow, and we have a theory that the new villain is someone familiar: it could be one of his adversaries from his canceled NBC series. Since his 2014-2015 solo series ended, Matt Ryan's fan favorite portrayal of the damned British warlock has refused to fade into the ether. After guest starring on Arrow to return the soul of the resurrected Sara Lance (Caity Lotz) - thereby forging his connection to the Legends - Constantine turned up again last season on Legends of Tomorrow, setting the stage for his jumping aboard the Waverider as a series regular. But it seems like the mage has brought along an unwanted villain that's hot on his tail and will also threaten his new time-traveling chums.

The Legends' season 4 mission of hunting down magical fugitives they accidentally unleashed throughout history was given to them by Constantine, but he himself initially refused to participate. That's because he seems to know exactly what it is that's out there, but in his typical keeping his cards close to his vest fashion, John isn't sharing this vital info with his new teammates in a misguided attempt to keep them "safe." And though he's now fitting in nicely aboard the Legends' timeship - except for how he ruffles the feathers of Mick Rory (Dominic Purcell), who loathes him - the trench-coat-wearing mystic is perpetually haunted, and with good reason, because something truly big and bad is on the way.

Related: John Constantine Changed Legends of Tomorrow For Season 4

Legends of Tomorrow's handful of season 4 episodes thus far have taken the misfit heroes to 1969 Woodstock, the 1692 Salem Witch Trials, and punk rock London circa 1977. All the while, the identity of the villain has been a deliberate slow burn. But the series has been carefully doling out clues about their mysterious new enemy, enough to make us suspect the entity that's coming for John Constantine is one fans have met before... on NBC.

Constantine Is Being Hunted On Legends Of Tomorrow

Constantine (and the fans) know that the self-styled master of the dark arts is being hunted because the unnamed villain literally announced it at the end of the season 4 premiere "The Virgin Gary". Fresh out of the shower and still very drunk, John was suddenly mystically possessed and then flung into a mirror. The culprit then wrote "I'm coming for you, Johnny" in blood red on the broken glass. The look on Constantine's face was one of recognition and maybe even inevitability - he knows who his adversary is.

Naturally, the secretive mage hasn't revealed this scary encounter to the other Legends, not even Sara. But his initial refusal of White Canary's offer to become a Legend was because everyone he calls a friend ends up suffering a horrible death, which is a fate he'd rather spare Sara, Ray Palmer (Brandon Routh), Zari Tomaz (Tala Ashe), Nate Heywood (Nick Zano), and even Mick Rory. Still, Constantine joined up with the Waverider's crew because he realizes he needs the Legends' help (even if he may be secretly manipulating them to get it), and if the enemy hunting him isn't something he believes he can handle on his own, it must be a horrible threat.

Who Is Hunting Constantine?

Constantine orders a coffee in Legends Of Tomorrow

Though Constantine hasn't clued the Legends in on who's hunting him, he's told and even tried to recruit other help against this mystery evil. In "Witch Hunt", when the Legends took on the Fairy Godmother (Jane Carr) who was causing anti-witch hysteria in 17th century Salem, the occult schemer offered a deal to the magical fugitive: he wanted the Fairy Godmother to bind herself to him as her human host and help him fight his enemy in exchange for John not banishing her to Hell. The Fairy Godmother, who knew exactly who John Constantine is and that he's a damned soul, outright refused and declared she'd rather face Hell and deal with "him."

So, it's clear the coming evil being is male, isn't from Hell (which rules out the Devil or the First of the Fallen), but is so terrifying that he's feared by other powerful magical beings. It's also clear the menace is someone from John's past because he said so to Zari in this week's episode "Disco Queen". However, fans can likely rule out that the threat are Constantine's parents, whom John and Zari met in a Liverpool pub in 1977, though both were unaware the drunken blond bastard in the trench-coat was their future son when John tried to kick his dad Tommy in the balls.

The biggest clue yet was a sudden flashback to the broken mirror with the blood-red writing that interspersed with an African face - if this is John's adversary, then he isn't Caucasian. All of this points to two major possibilities from Constantine, the failed NBC show, and the dangerous enemies who have unfinished business with John: Manny the Angel and Papa Midnite.

Page 2 of 2: Constantine's NBC Villains Could Have Followed Him To The Arrowverse

Manny & Papa Midnite's Role in Constantine Season 1

In the Constantine series finale, Manny (Harold Perrineau) revealed his true nature as the villain behind the Rising Darkness that John was facing. Manny is an angel and a purported Soldier of Heaven who told John that he was sent to watch over him and guide him against the great threat called the Rising Darkness, but it turned out Manny was orchestrating the darkness all along. Manny was secretly trying to bring about the end of Mankind, and he was the being who controlled the Brujeria, a Chilean-based sect of evil warlocks trying to merge the Earth with Hell. For mysterious reasons, Constantine was a key component in this plan, so much so that Manny canceled the contract on John's soul and declared him off limits at the end of the series - although Constantine is still damned.

As for Papa Midnite (Michael James Shaw), he is a voodoo priest and enemy of John Constantine. They tangled over the acetate, a vinyl recording that contained the actual voice of the Devil. Midnite later failed to have Constantine killed by the Brujeria before Manny freed him from police custody and recruited a reluctant Midnite to aid the Rising Darkness. Since Constantine's cancelation, the plot thread of the Rising Darkness has been left hanging - but in the 3 years that have passed, Constantine has been folded into the Arrowverse and the events of the NBC series are believed to have occurred on Earth-1. This means Manny and Papa Midnite are still out there and could return. Hence, one or both of them may be en route to face John Constantine on Legends of Tomorrow.

What Manny & Papa Midnite's Possible Return Means

John Constantine and Sara Lance talk on Legends of Tomorrow

With John Constantine fully ensconced in the Arrowverse, it makes sense that other characters from his NBC series could join him as well. However, the face briefly shown in "Disco Queen" didn't belong to actors Harold Perrineau (Manny) or Michael James Shaw (Papa Midnite), so if one of those original Constantine villains is Legends of Tomorrow season 4's villain, then the role may have been recast for The CW. It's also possible that the enemy is an entirely new threat that still has ties to John's morbid and tragic past. After all, the British exorcist and demonologist has no shortage of occult enemies who want him dead.

If the villain is Manny or Papa Midnite, though, then it's another example of how the Arrowverse is expanding to include other DC TV series as part of The CW's shared multiverse. The upcoming Arrowverse crossover Elseworlds (which Legends of Tomorrow won't be part of) is establishing that 1990's The Flash TV series is part of the multiverse. It only makes sense that Constantine is also, although in a different way, since it's part of Earth-1 and didn't happen in its own Earth/reality. But theoretically, any character Constantine met in his own series is fair game to appear in Legends of Tomorrow (though they may have to be recast).

As for the Legends, Manny or Papa Midnite coming for John Constantine could inject a degree of horror into season 4 that the time-tossed goofballs may be ill-equipped to deal with. The series has only leaned further into their distinctive brand of weird, irreverent comedy as they chase mystical fugitives across the timeline. If the theory holds and Constantine's Rising Darkness has followed him to Legends of Tomorrow, their zany adventures could suddenly pivot into something truly frightening - and they'll need a comforting hug from Beebo more than ever.

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DC's Legends of Tomorrow airs Mondays on The CW.