The Flash: What Is Eternium?

Every season of The Flash has a Harrison Wells. It's one of the show's constants beginning with Season 1's "Harrison Wells" that was really Eobard Thawne in disguise. Since then there have been many versions of what may just be the smartest man in the Multiverse, though last season's Sherloque has since departed Earth-1 making room for a new version to arrive. He does so in tonight's episode of The Flash, but rather than coming to Central City to be part of Team Flash, this Harrison Wells has his own agenda. That agenda includes looking for items containing something pretty specific -- Eternium.

But what is Eternium? For fans of DC Comics it might ring a few bells. First appearing in Legion of Super-Heroes (Volume 4) #110 in 1998, Eternium is the name that was given to shards of matter that were cast when the Rock of Eternity was destroyed. The Rock of Eternity, fans may recall, was the lair of the wizard Shazam -- yes, the same wizard connected to that Shazam. In comics, Eternium is a powerful thing. Being near it removes the Powers of Shazam and actual physical contact with it leads to injuries. It's serious business.

It's not clear exactly why Nash Wells (Tom Cavanagh) is looking for particles Eternium. His first encounters with Cisco and Iris don't go particularly well, first with Nash attacking Cisco and threatening with a nightmare-inducing ruby that sounds quite a bit like the ruby Morpheus used to manipulate dreams and then, later, disappearing in the cloud of a smoke bomb after waking up in Iris's office. He does reveal that he's looking for the Eternium, though having gotten a reading off of Iris. Beyond that, Nash reveals nothing else (well, he's in the business of "debunking" myths), though with "Crisis on Infinite Earths" rapidly approaching, it wouldn't be a huge surprise if Nash's hunt for Eternium somehow plays a role. It appears he's going all over the Multiverse looking for the Eternium, after all, and the Multiverse is what's in grave danger.

"Crisis turned out to be the best thing that could have happened to…The Flash because it created an immediacy to things," The Flash showrunner Eric Wallace said after a screening of the season premiere. "We know that on December 10, 2019, the Flash will die….We're not messing around."

While Nash Wells' quest for Eternium may have something to do with the coming "Crisis", we also know that Cavanagh is also playing a second character this season as well, Pariah, a character integral to "Crisis" in comics.

"In the original miniseries, it's Pariah who is very much integral in releasing the Anti-Multiverse. For Tom to play such a pivotal character... it's just going to tear your guts out and make you cry," Wallace said earlier this year.

Wallace wouldn't divulge the reason behind Cavanagh's new role, as it is scheduled to be revealed at the end of the first "graphic novel." He teased that these developments, "lead up to a very, very big twist at the end of the Bloodwork case that launches 'Crisis.'"

The Flash airs Tuesdays at 8/7c on The CW.