Since the earliest days of DC's Rebirth era, one of the biggest mysteries has revolved around the mysterious Mr. Oz and his connection to Doctor Manhattan and the conspiracy that took ten years of the DC Universe’s history away from its heroes. Mr. Oz, who has been capturing heroes and villains alike that could ruin his plans, currently has Red Robin in his clutches, but much has been made of one of Tim Drake’s fellow prisoners; a mystery character that DC promises will shock and surprise us when they are revealed later this year.

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DC Rebirth has done an excellent job of bringing the DC Universe back to something more familiar and loved by longtime fans, while keeping newer readers intrigued and interested. Much of that has been accomplished though the return of many fan-favorite characters, but there’s still a lot of people unaccounted for that Mr. Oz would want off the table for one reason or another. We’ve taken a look at the candidates, and think we have an idea of who the surprise cellmate may be.

The Easy Bets

While Tim Drake’s imprisonment and subsequent journey to freedom has been documented in Detective Comics, much of the mystery surrounding Mr. Oz himself has taken place in Action Comics, which has recently gone through a continuity upheaval in order to bring Superman back to his his post-Crisis/pre-Flashpoint status quo (more or less). However, one major character was noticeably missing from Superman’s backstory: The Boy of Steel, The Metropolis Kid himself, Superboy, AKA Kon-El, AKA Conner Kent. When DC Rebirth was announced, Chief Creative Officer Geoff Johns said the lack of a familiar Superboy was the first sign things had gone wrong with The New 52, so we expect him to be a big part of the Rebirth plans going forward. As for why he might be here, Kon has the advantage of being Tim’s best friend, so it would make sense of them to be able to work together to escape Mr. Oz's clutches.

Superboy-Kon-El

Another one of Tim’s closest friends has been missing since The New 52 -- Bart Allen, AKA Kid Flash, AKA Impulse. Bart merged with The Speed Force at the end of Flashpoint to become the White Flash, and although there was a Kid Flash named Bart Allen in The New 52, it was revealed to be an imposter war criminal with no connection to the real Bart or the Allen family. Every major continuity shift in DC history has had The Flash family at the heart of it, so this would be a perfect time to bring back Kon, Bart, or the pair of them, and reunite the original Young Justice.

Time and Space

Mr. Oz seems to want to keep people off the board who might reveal the false reality Doctor Manhattan helped create, and there’s a number of heroes and villains who exist outside the natural flow of time who he would likely target to maintain his position. If we’re still thinking of Flash-related characters, then Hunter Zolomon, AKA Zoom, would be able to dance between the raindrops of continuity and see the changes. Or a character like Monarch, who lives outside of time, might not appreciate someone stealing his bit.

Booster-Gold

If the events of DC Rebirth and Doomsday Clock are to be Crisis-level continuity shake-ups, then we may well see the return of Pariah as Mr. Oz’s prisoner, a character who always finds himself in the wrong place at the wrong time in these occasions, destined to warn the heroes of the DC Universe of major upheaval. One character who would be able to put a stop to it, but wouldn’t be missed if he disappeared, is Booster Gold, who hasn’t been seen since Convergence. His role as protector of the timestream would make place him high up on Mr. Oz’s list of threats to deal with.

The Past and The Future

We know that at some point the Justice Society of America and the Legion of Super-Heroes are going to play a part in the larger DC Rebirth story. Jay Garrick briefly returned in the recent Batman/Flash crossover “The Button,” while a Legionnaire presumed to be Saturn Girl is currently locked away in Arkham Asylum and longtime Legion foe Emerald Empress has been tormenting Supergirl. While we don’t know what has sealed these two teams off from the present day DC Universe, it does seem like the kind of thing Doctor Manhattan would do in order to isolate the heroes of the DCU's moderne ra and rob them of their families and personal relationships. Plus, Mr. Oz’s fortress exists outside of space and time, so he could easily nab heroes from whatever era they pose a threat from.

Brainiac-5-Legion-of-Three-Worlds

It’s possible that Brainiac 5 figured out something was wrong in the past and Mr. Oz took him prisoner to stop him from learning more. Or perhaps the time-traveling Starman — a favorite of Geoff Johns and a member of both the JSA and the Legion — holds the secret of the Doomsday Clock somewhere in his fractured mind. There’re plenty of reasons to take both the JSA and the Legion off the board, and it wouldn’t be too out there to see any one of them show up as Mr. Oz’s captive.

Gods and Men

Like any great comic book reality, the DC Universe is home to a great number of cosmic entities, and if any of one of them were captives of Mr. Oz alongside Tim Drake, it would go a great way towards showing the seriousness of the threat he poses and the power he possesses. While we haven’t seen Doctor Manhattan fully in the DC Universe yet, we did see the character Pandora — the symbol of The New 52 if there ever was one — obliterated in an alley in a way intentionally reminiscent of the way Manhattan kills Rorschach at the end of Watchmen.

Pandora's death in DC Rebirth

Just imagine if Tim Drake gets out of his cell and finds that his cellmate is someone like The Spectre or The Phantom Stranger, and what that says about Mr. Oz and the odds Tim needs to overcome to escape. It’s a simple narrative trick to establish a villain, but it would be a super-effective one and bring Detective Comics into the cosmic scope of the larger story in a way that it hasn’t yet been.

The Dark Horse

Then there’s my personal pick. The character no one has yet considered, someone whom everyone underestimates and who has the ability to blow the whole thing wide open. Imagine you’re Mr. Oz, and you’re scooping up DC Comics heroes and villains who might expose you. You’re planning an elaborate conspiracy -- a cover-up, even -- that revolves around stealing literal years of happiness from the world’s greatest heroes. Which hero is most likely to notice something is wrong, and which hero will no one notice is missing?

That’s the Question, isn't it?

Vic Sage, AKA The Question, is a character in need of a massive post-New 52 rehab. As part of the New 52 reboot, the concept of The Question was reintroduced as a mystical entity, part of The Trinity of Sin alongside Pandora and The Phantom Stranger. Vic Sage, however, was reintroduced as a government stooge who took over the Suicide Squad from Amanda Waller, only to fill it with even more volatile components. The Question as a concept is broken right now, and this story would be the perfect way to bring him back to prominence in a big way.

RELATED: DC Rebirth - Mr. Oz’s Identity Will Be Revealed in September

The Question would sniff out any cover-ups, no matter how cosmic, so he would be the perfect candidate to be the first person Mr. Oz took off the board when the universe was remade as The New 52. Of course, to maintain the cosmic balance, Oz would have made sure there was a Question and a Vic Sage to fill in the blanks, even if they weren't the Question and Vic Sage. It’s a longshot guess, sure, but he’s a character that would fit in perfectly with James Tynion IV’s Detective Comics run, and makes perfect sense as Tim's secret cellmate.