Dark Nights: Metal began with a mystery. An investigation by Batman into a mysterious alloy lead him to questions he'd never known to ask, and answers he wishes he never needed to learn. Over the course of Scott Snyder and Greg Capullo's event series, the Dark Knight's investigation into the Dark Multiverse has left readers with a few lingering questions of our own. And, like all mysteries, the biggest questions start at the beginning, where Dark Days first led into Dark Nights.

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Before Metal arrived, DC Comics published two prequel one-shots to set the stage for the event. Those two comics, scripted by Snyder and illustrated by a roster of A-list artists, were called Dark Days: The Forge and Dark Days: The Casting. While those issues set up many important beats that Metal has since picked up on, there are a few pieces of the picture that have yet to be filled in.

What Is Duke Thomas' Connection to The Immortal Men?

Duke Thomas, aka The Signal, figures prominently in The Forge and The Casting, where he investigated a mysterious room in the Batcave alongside Green Lantern Hal Jordan. Their scene transitions into a preview of the forthcoming The Immortal Men series, with the Immortal Man himself talking about Duke's own mother.

The new Immortal Men

Back during the events of "Batman: Endgame," Duke's parents were rendered permanently insane by the Joker and are currently being taken care of while Batman searches for a cure. The Immortal Man reveals that he has been monitoring Elaine Thomas, Duke's mother, and that he had at one time actually offered her a place among the ranks of the Immortal Men.

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So, what does this have to do with Duke? We know he now has superpowers, as established first in The Casting, and currently being expanded upon in the Batman and the Signal miniseries, but how does that relate to the Immortal Men? This brief scene could have shown the Immortal Man watching anyone in the DC Universe, so the answer as to why it focused on Duke's mother will likely play a big role in Metal's conclusion.

Where Will the Outsiders Show Up Next?

In The Casting, Duke and Hal walk down a corridor of conveniently placed holograms while Joker to explain Batman's investigation of Nth Metal. The clown reveals that the Dark Knight established his own team that could investigate these mysteries in secret, while a hologram shows that team to be the Outsiders.

The Outsiders return in 'Dark Days: The Forge'

Metal establishes them to be something of a black ops team for Batman, consisting of Black Lightning, Metamorpho, Katana, Halo and Geo-Force. While most of these heroes have been missing since the beginning of Rebirth, Katana has been a prominent member of the Suicide Squad, and Metamorpho is set to feature in the upcoming Metal spinoff, The Terrifics.

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Knowing what is to come, and the fact that we haven't seen this team in action in Rebirth continuity, we have to wonder where they've been and what they've been doing.

In The Casting, Batman attempts to contact Black Lightning when he comes across a secret base in the Arizona desert. He mentions he wants his people to investigate the place and find out who runs it. Just then, he encounters the psychic mutant Dubbilex, long a part of the mysterious clone-creating Project Cadmus, who tells him that some organization has been experimenting on people by exposing them to the metal. Based on the psychic image he implants in Batman's head, these are the people who created the monster Damage, who just launched his own ongoing series. Will the Outsiders continue their investigation into the matter there, and will Project Cadmus become a major player in the DCU once more?

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When Will We See Shazam Again?

The superhero Shazam has been missing since the start of Rebirth, and there doesn't seem to be any clear plan to reintroduce him anytime soon. That hasn't stopped Scott Snyder from introducing the Wizard into the events of the series, even if he has a very small role.

Hawkman outlines in his journal that the Wizard once owned an Nth metal dagger. Carter Hall later used that dagger to journey into the Dark Multiverse, and now Batman is after the same artifact in order to continue his investigation. While the dagger itself is simply something of a MacGuffin, the fact that it comes from the Wizard and brandishes the Shazam symbol can't be ignored.

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Despite the tease, it doesn't look like Shazam will be making an appearance in Metal, but it could be a setup for something else. The Wizard is seen to be a member of the immortals, and is therefore associated with the Immortal Men. The dagger was also used to send the Challengers into the Dark Multiverse, so could the Wizard and Shazam factor into the The Immortal Men or New Challengers (written by Snyder himself) series following the events of Metal?

What Roles Do Metals One Through Eight Play?

Metal has revealed that Nth metal is actually the ninth iteration of the mysterious metal that Batman has been tracking. In The Casting, Wonder Woman gives Batman the Sunblade, a sword made by Hephaestus that is said to be composed of "the eighth metal." While it is powerful in its own right, it is not as pure as the Nth metal that Batman is seeking. Wonder Woman also mentioned that the Sunblade was one of 12 weapons crafted by Hephaestus for Greek Pantheon of gods.

This dialogue leaves us with several implications. If the eighth metal is less pure than the ninth, that means there are seven other iterations of the metal, presumably with varying levels of power.

Batman then trades the eighth metal to acquire the ninth from Talia al Ghul, but what becomes of the Sunblade and the lesser metals? Considering Talia mentions The Silencer in her scene with Batman, and is expected to appear in the Silencer's new title, could she be giving her assassin a new mission to gather these weapons?

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What Does the Joker Have to Do With All of This?

In The Forge, Duke and Hal find the Joker locked up inside a secret section of the Batcave, but we never learn exactly why he was there. It is implied that he's been locked up for some time, and he knows all about Batman's secret investigation of the metal. What's even weirder is that he seems to genuinely see himself as the hero trying to stop Batman from going too far.

DC Comics The Forge Joker

After the Joker makes his escape, Batman shows up and says that he needed to keep him imprisoned for something, but what exactly is never actually revealed. Was the Joker going to visit the Dark Multiverse? Were the two investigating the metal together? He has yet to turn up in the actual miniseries, so it's hard to say exactly what kind of role the Joker has to play in all this.

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It's also worth mentioning that we may never get an answer from Scott Snyder, because it's might not be his story to tell. Hal Jordan wonders aloud if this is even the real Joker, and it's fair to acknowledge the idea that this is an imposter as a possibility. Geoff Johns introduced the idea that there were three Jokers running around in the DCU, so what if this is one of them? We may have to wait to find out the answer to that in the pages of Doomsday Clock.

What's In the Plastic Man Egg?

One of the biggest mysterious of Metal has been the presence of Plastic Man. Batman needed his Justice League cohort's unique molecules to power his Dark Multiverse viewer, but it was also stated that he was unstable and needed to be contained. Since showing up in The Forge, Plans has remained only a semi-sentient egg with a mysterious role in all of this.

the plastic egg

In the pages of Metal, Mr. Terrific took the Plastic Man egg into outer space to check out Hawkworld, but there hasn't been any indication as to what kind of role he is supposed to be playing. Plus has been promoted as a member of The Terrifics, but strangely, the preview to issue #1 still depicted him in egg form.

It's also worth asking about what exactly is inside the Plastic Man egg anyway. Maybe Plas is simply evolving, or perhaps he's holding someone inside, like his son Offspring, or Phantom Girl, another member of The Terrifics. Given the fact that the new title will be dealing with the disappearance of Tom Strong, could he contain something to do with him? For all we know, the character's multiverse traveling Search Board is inside.

The best mysteries don't always give you all the answers, but in this case we could use a little more information. Hopefully, we'll learn more as Dark Nights: Metal comes to an end, though it's likely some questions won't be solved until we're a bit deeper into the New Age of DC Heroes.