New posters for this winter’s Kamen Rider mega-crossover event, Kamen Rider Heisei Generations FINAL: Build & Ex-Aid with Legend Riders, have surfaced, and we’ve got our microscopes handy for some good old-fashioned speculation about what these images could mean for the landmark film. As the headlining Kamen Rider Build takes center stage as the final Rider series of this decades-long franchise to air during Japan’s Heisei Era, this can be seen as the closing chapter of an epic saga. At least until next year, where we inevitably start all over again.

First, the beautious new posters for the film, featuring the star-studded cast of superheroic figures of past and present, among which are a few actors that many Rider fans never believed they’d see again.

Oh yes.

From left to right, we have Fukushi Sato as Gentarou aka high school student-turned-teacher Kamen Rider Fourze, Nishime Shun as Takeru aka dead-turned-living spiritualist Kamen Rider Ghost, Inukai Atsuhiro as Sento aka genius amnesiac Kamen Rider Build, Iijima Hiroki as Emu aka doctor gamer Kamen Rider Ex-Aid, Sanno Gaku as Kouta aka dancing fruit god Kamen Rider Gaim, Watanabe Shu as Eiji aka wandering coin-flipper Kamen Rider OOO, and Miura Ryosuke as Eiji’s antiheroic buddy Ankh.

What a crew. They stand together in a wrecked cityscape, but what I found most interesting upon taking a closer look, is what appears to be something far above them. An image that recalls a few others in Kamen Rider past.

First, there was the moment in Kamen Rider Decade, in which the title hero Tsukasa is suddenly confronted with a second Earth that was brought, via a strange dreamlike vision, right up close to the one he’s standing on. So Decade is literally standing on one version of the planet while looking up at another version that is so close he could jump over to it. Years later, we saw the ominous image of a world unraveling, as the land of the dead sought to overtake the living realm, peeling back the Earth’s layers like a piece of fruit.

In both instances (among others), there was a city in the sky, hanging upside-down like a stirring reflection. Foretelling a shift that would see the world as we know it succumb to some kind of supplementation by another. We see cities, roads, rivers, and bridges hovering above a whole other set of them. And in-between these two massive structures stand our heroes, as if preparing for the battle that must be waged to stop whatever this portends.

Of course, it could just be some symbolic gesture. Like it’s a reflection of what’s at stake if the Riders and their allies fail. But we could be seeing a return to some of these visual and narrative themes, even if just by pure accident.

And here we have the other poster, a transitional play on the first. The heroes have had it up to here with the enemy and have suited up for combat, with a blazing orange glow overhead and an army of villains at their back. Without a Rider suit of his own, Ankh has perhaps gotten the hell outta dodge, at this point.

But it’s that army that fascinates me most. Nihon Hero provides this closer look at the apparent robot brigade threatening the Riders:

Are we looking at modified Guardians from Kamen Rider Build? Or some other foot soldier altogether? Either way, the X on their armor might suggest the return of Foundation X, the mysterious shadow organization that has haunted the Riders of the new Heisei Era from a distance for years.

First appearing in Kamen Rider W (which itself has seen another surge in exposure with the Fuuto Detectives manga series and photoshoots with the actors, giving rise to even more speculation about the sudden interest in this incarnation), Foundation X helped fund the Sonozaki crime family’s research into the dangerous Gaia Memory program, granting users with monstrous powers that could be valuable to a group with world domination on their to-do list.

Despite their best efforts, the Riders have only ever managed to delay the growth of Foundation X, as they continue to dip their fingers into everybody’s pie, snatching up information and power from the Medals of Kamen Rider OOO and the Cosmic Energy Switches of Kamen Rider Fourze, as well as other appearances that reveal their secret involvement in what had previously seemed entirely disconnected.

I’ve loved the concept of Foundation X since it was first introduced. A villain that could unite every wacky, unrelated concept this gigantic franchise could throw at us and pull the whole unwieldy mess into one story. Of course, it’s clunky and impossible to make complete sense out of, but it’s a fun way of suggesting that, no matter how far apart Kamen Rider’s many worlds seem to be, there’s something that still connects them. And not just the “spirit of justice” or whatever. There’s a bad guy that overrides all others and sticks around longer than any one series. The old school Showa Era had Shocker. This one has Foundation X.

And what a time for Foundation X to return, as we say our last goodbyes to this leg of the journey. The “X” always seemed to signify the sort of unknowable quality of the organization- something that couldn’t ever fully be uncovered or explained. Just something there out of the corner of your eye, after you’ve forgotten it could even be there. But now, it could mean something more literal.

If we count W as the first, Build is the ninth series of this section of the franchise. If we count W’s predecessor, Decade, it’s the tenth. And given this section’s love of numbers and number-based symbology (seriously, you could make yourself sick looking at all the weird ways an object or a logo represents millions of possible things all at once), it might be fitting to save the world from the “ten” villain. The unbeatable, unquantifiable enemy that was always building us toward this end.

Or, you know, the monster designers just thought the “X” looked cool that day. Whichever.

Kamen Rider Heisei Generations FINAL: Build & Ex-Aid with Legend Riders strikes its final henshin pose December 9, 2017. With so many appearances from Kamen Rider’s acting elites, let’s hope the film’s running time is at least as long as that epic title.