Warning: SPOILERS through Justice League #2.
The latest issue of Justice League has unveiled the existence of The Still Force - a hitherto unknown energy born of inertia, that serves as an equal and opposite counter to The Speed Force utilized by The Flash. The Still Force was revealed to be one of seven hidden universal forces, whose mastery is required to save the DC Universe from falling to entropy.
First introduced in The Flash #91, The Speed Force was meant to hand-wave most of the scientific questions regarding how The Flash's powers functioned. It was revealed that The Speed Force created a force-field that prevented a speedster from feeling the effects of friction as well as fueling their powers so that speedsters didn't burn through all the calories in their body. The Flash: Rebirth later revealed the existence of a Negative Speed Force, utilized by The Reverse Flash, which offered many of the same powers as The Speed Force, but with a greater potential for destruction.
It would seem, however, that this was another aspect of The Speed Force and that The Still Force is the true "reverse" of The Flash's energy source.
Appropriately enough, the nature of The Still Force is revealed slowly across the course of Justice League #2. It begins with Lex Luthor explaining the existence of the seven hidden forces to his colleagues in The Legion of Doom. Luthor claims that the team's membership have each been searching for these forces for years, despite not knowing that was what they were doing.
Luthor then reveals that he has already unlocked the first force - which Grodd can use to destroy The Flash once and for all - and that Green Lantern Corps villain Sinestro is already en route to claim the second. Curiously, the secret of this first force lies with a newborn human baby, whom Luthor claims is "a true evil genius."
A later scene sees The Flash working with Hawkgirl on building a car that can tap into The Speed Force. As they work together, Hawkgirl asks The Flash if there was any reason why he seemed to keep tripping-up during their most recent battle. The Flash confirms that The Speed Force had briefly failed him and he blames this upon a supervillain called The Turtle, who he claims was obsessed with finding a theoretical Still Force that could counter The Speed Force. While unsuccessful, The Turtle still managed to create "vibrational disruptions" that momentarily disrupted The Flash's powers.
The final relevant scene reveals Green Lantern John Stewart in deep space, as he is exploring the area around the weakening cosmic membrane. It is revealed that Stewart knows something of the "hidden forces" that Luthor spoke of earlier and he reports to The Guardians of The Universe that it seems that The Still Force has been unlocked. He then discovers what was contained on the other side of the cosmic membrane - the second hidden force, an emotional spectrum of invisible light based on emotions kept hidden, which has already been claimed by Sinestro!
This invisible emotional spectrum had already been revealed by earlier reports that John Stewart would become an Ultraviolet Lantern. It is unclear precisely how this ties into The Still Force and what connection it has to the baby. One likely guess is that The Turtle used The Still Force to reverse his aging - a trick utilized by some speedsters in the past. In any event, things are about to become very interesting for The Flash and the Justice League.
Justice League #2 is now available from DC Comics.