The latest episodes of the Arrowverse ended with a dramatic teaser setting up the "Elseworlds" event featuring the 1990s Flash and the Monitor. This is probably the most exciting Arrowverse crossover to date, bringing together the heroes of various different realities and serving as a back-door pilot for the Batwoman TV series. It promises to redefine the Arrowverse's understanding of their multiverse, with this first clip already revealing the existence of Earth-90.
Jeremy Davies has been confirmed as the main villain of "Elseworlds," a character named Dr. John Deegan. He's been described as a doctor at Arkham Asylum who's every bit as insane as his patients, but it's as yet unclear how Deegan will come to trigger a Multiversal catastrophe. One popular theory suggests Deegan is an alias for Batman villain Dr. Hugo Strange, while another posits that he's really the telepathic villain Dr. Destiny. Whatever the truth may be, DCTV is evidently keeping Deegan under wraps right now; he doesn't feature in this first teaser, which instead focuses on establishing the sheer scale of the "Elseworlds" event.
The Supergirl stinger scene is set on Earth-90, home of the Flash from the 1990 TV series. It reveals a host of fallen superheroes who presumably allied with the Flash against a terrible threat; attentive viewers will recognize versions of Green Arrow, Firestorm, The Ray, Hawkman and Hawkgirl, and even Stargirl. Unfortunately, they've all fallen in battle - indeed, some of the deaths look particularly brutal. John Wesley Shipp's Flash seems to be the last surviving hero, and he confronts the cosmic being known as the Monitor.
The Flash's pleas for mercy fall on deaf ears, as the Monitor insists that the heroes - perhaps the entire world - "did this to yourselves." The Monitor opens a mysterious book, unleashing cosmic energies, but the Flash races away - presumably jumping out of his world, and on to another. It seems this brief clip has revealed the destruction of Earth-90 - and it's safe to assume the heroes of Supergirl, Arrow, and The Flash will wind up uniting with Shipp's incarnation in an effort to stop the devastation being repeated.
This teaser raises countless questions. Even the designation of this doomed world as Earth-90 is a shocking one; the Arrowverse has previously established that there are only 52 Earths in its Multiverse, with the addition of Earth-X. It looks as though everything the shows have established as the Multiverse may well be wrong. Meanwhile, the glimpse of the Monitor as an apparent villain is somewhat surprising; he's normally portrayed as an ally to the heroes. It's possible this stinger is misleading, and that this is the Monitor's evil and destructive counterpart, the Anti-Monitor. In the classic "Crisis on Infinite Earths" event, it was revealed that the Anti-Monitor was destroying entire universes, consuming them as fuel to increase his power; perhaps something similar is happening here. But what is the book held by the Monitor/Anti-Monitor? At this stage it's difficult to say, but it's possible it could be the Book of Destiny. Strongly associated with the Sandman comics, this book contains the written record of everything that is and ever will be. If this is indeed the case, it could be the most powerful artifact the Arrowverse heroes have ever encountered.
This year's Arrowverse crossover remains something of a mystery. It's known to involve a body-swap for Flash and Green Arrow, one that sees them head to Supergirl's reality for help (for undisclosed reasons). Exactly how this ties into the destruction of Earth-90 is unknown, suggesting there will be a lot of unexpected plot twists over the course of the event.
Arrowverse's "Elseworlds" event begins with The Flash on Sunday, December 9 at 8pm ET, and continues with Arrow on Monday at 8pm ET and concludes with Supergirl on Tuesday at 8pm ET.