WARNING: SPOILERS through Justice League #4

Once, Sinestro was the most well-respected member of The Green Lantern Corps, before he forsook the power of Will and established the fear-empowered Sinestro Corps. The latest issue of Justice League sees Sinestro go one step further, taking command of an hidden power and, through it, the largest Lantern Corps in the history of the universe!

The multiverse of DC Comics has been in a a state of shock following the events of Dark Nights: Metal. The destruction of The Source Wall - the barrier between this reality and the next - unleashed unfathomable energies and cosmic secrets that were never meant to be known. One of these secrets was the existence of Umbrax - an evil sentient sun whose light generated an Invisible Emotional Spectrum that acted as an equal and opposite force to the Emotional Spectrum which The Green Lanterns, The Sinestro Corps and all of the other various Lantern Corps drew upon to fuel their powers.

Coincidentally, a young Sinestro, who had been an anthropologist before he was recruited to join The Green Lantern Corps, had studied what few legends regarding Umbrax existed and sought to determine the truth of its powers.

Related: Secret Origin of Sinestro (Before Green Lantern) Revealed

It has been revealed that the Invisible Emotional Spectrum differs from the Emotional Spectrum in two key respects. The first is that the Invisible Emotional Spectrum draws upon negative repressed emotions, such as Shame and Lust, rather than Hope or Love. The second is that a person tapping into the Emotional Spectrum generally has the ability to control their emotions and, through it, the energies that The Emotional Spectrum generates.

By contrast, those who develop a connection to the Invisible Emotional Spectrum become a slave to their own worst impulses, with the power controlling them instead.

The current run of Justice League has seen Lex Luthor form a new group dubbed The Legion of Doom. Despite the sinister name, which Luthor based off the classic definition of "doom" meaning an inescapable fate, the group is devoted to stopping the accelerated breakdown of the multiverse by mastering seven fundamental energies.  The first of these energies is The Still Force - a power based around inertia, that acts as a counter to The Speed Force that empowers The Flash and other speedsters.

Thanks to the efforts of The Legion of Doom, The Still Force is strengthened, which halts the expansion of the universe and weakens the cosmic membrane holding Umbrax in check. This further allows Sinestro, who found a way to harness the power of the Invisible Emotional Spectrum without being taken over by it, to assert his will over The Earth and the planets already under Umbrax's control. He then starts recruiting all the people of Earth who are ruled by self-loathing as foot-soldiers for his Ultraviolet Lantern Corps.

Precisely why Sinestro needs an army of mindless thralls with a power exceeding that of the Green Lantern Corps is unclear. Doubtlessly this is all a part of Lex Luthor's master plan to save the multiverse but it's unlikely the Justice League will approve of the apparently reformed Luthor's actions. Of course with the power Luthor and The Legion of Doom now command, it seems there is little The League can do to thwart their designs.

More: The REAL Reason The Justice League Needs John Stewart

Justice League #4 is now available from DC Comics.