Zack Snyder, who directed the DC Extended Universe movies Man of Steel, Batman v Superman: Dawn of Justice and Justice League, has added new information about the infamous “Knightmare” scene, including the fact that it involved the Cosmic Treadmill.
The sequence, seen in the middle of Batman v Superman: Dawn of Justice, featured Bruce Wayne/Batman (Ben Affleck) having a nightmare about some kind of dystopian future where he led a group of rebels against an evil Superman. It ends with Barry Allen/the Flash (Ezra Miller), whom Batman has yet to actually meet, appearing and yelling that Lois Lane (Amy Adams) was “the key” (to preventing this from happening, presumably).
This makes little or no sense within the context of the movie, and was apparently meant to be foreshadowing for a later film. Originally Snyder was planning to direct five DCEU films, which would have included a two-part Justice League; fans generally assume that the unmade “Part 2” would have featured the “Knightmare future,” and that the Flash had traveled back in time to warn Batman about it.
As reported by Screenrant, the new comments, made on Snyder’s Vero account, seem to confirm this. He mentions that, in the “Knightmare future,” Batman and the Flash sneak into the Batcave in order to reach past-Batman, even though they know they could be easily found there. However, Barry apparently went farther back in time than intended, before past-Batman knows enough to understand it’s significance.
“But he is ‘too soon’ meaning he went [too] far back, meaning he will have to step off the ‘cosmic treadmill’ one more time,” Snyder wrote.
In the comics, the Cosmic Treadmill is a device that can harness the Flash’s super-speed to allow him or other characters to travel through time. It originally premiered in December 1961’s The Flash #125; curiously, it’s origin has never been explained, but perhaps would have been an invention of Batman’s in the DCEU.
All in all, the “Knightmare” wound up being pretty pointless in the finished films; Batman never mentions it, even when he befriends Superman (Henry Cavill), Lois and the Flash, and while Lois does manage to quell a temporarily-insane Superman in Justice League, Snyder was obviously intending more for this story. With him active on social media, however, fans can at least get hints on what his plans were.