'The Flash' Name Drops a Surprising Villain From 'Dark Nights: Metal'

Tonight on The Flash, fans may have heard the show tease an upcoming villain -- and if so, "Crisis on Infinite Earths" will not be the only upcoming story to make use of the darkest and most dangerous corners of the DC multiverse.

And, no, we aren't even talking about the Mad Hatter, who gets repeated references in this episode and now feels like a pretty solid likelihood as a villain who might appear in the first season of the planned Batwoman series coming to The CW next season. Rather, we're talking about something to really test Barry's mettle...or is it Metal?

When the younger Nora, in her memories, stands before a kiosk at the Flash Museum, Cicada's story is chilling: after Barry Allen disappeared in the Crisis, Cicada returned and continued his killing spree. His death toll was compared to the likes of other killers from The Flash's history, like Zoom (the season 2 big bad) and Red Death.

Which...wow. That's a thing.

The Red Death is a version of Bruce Wayne who managed to connect himself to the speed force. If you are a Batman fan but have not read Dark Nights: Metal, that might not sound all bad. But Metal was the line-wide crossover that saw an army of "Dark Knights" -- Batmen from the Dark Multiverse who had been mashed up with other Justice Leaguers, usually after having mudered their Earth's version of whoever they got the powers from.

Here's how the DC Wiki breaks the character down:

The Batman of Earth -52 once fought crime with the help of his sidekick Robin. Unfortunately, as time went on, many different Robins lost their lives during various missions with the Caped Crusader, which drove him to adopt more extreme methods towards crime-fighting.

When Earth -52 was on the verge of destruction, Batman, using the weapons of the Rogues (Captain Cold's freeze ray, Heat Wave's heat gun, Mirror Master's mirror gun and Weather Wizard's wand) fights the Flash, who had refused to give him Speed Force powers.

After knocking Flash out, Batman chains him to the hood of the Batmobile (which he had modified using the designs of the Cosmic Treadmill) and drives him and Flash into the Speed Force.

As a result, Batman and Flash are forcibly fused together into one being, with Bruce gaining Flash's powers and a corrupt connection to the Speed Force while Barry's consciousness became trapped inside Bruce's body.

With his new abilities, Batman quickly murdered his own rogues gallery, although realized he was still too late to save his world from destruction. Bruce is then visited by The Batman Who Laughs, who tells him that he can still save his world by joining Barbatos' Dark Knights and aiding the deity in conquering a Multiverse above their own. Batman accepted his counterpart's offer and became known among the group as The Red Death.

The idea of Red Death being mentioned is a particularly interesting idea given that we only recently learned that Batman is definitely a thing that exists (or existed) in the Arrowverse, meaning that the character could theoretically exist in the same space as Barry.

Whether this, like season three's mention of The Thinker, will pay off shortly or not is anybody's question.

The Flash airs at 8 p.m. ET/PT on The CW.