Warning: The following contains spoilers for The Flash #775, on sale now from DC.
The Infinite Frontier era kicked off with Wally West leaping back into his role as the Flash as his mentor Barry Allen went off on his own mission across the reborn DC Multiverse. And for the veteran superhero, defending Central City once again as its Fastest Man Alive is just like falling into old rhythms for Wally, balancing his superhero responsibilities with a new day job and his life as a family man to a wife and two young children. But when an old Justice League supervillain resurfaces in Central City, Wally finds his entire hometown has fiendishly turned against him as scrambles to stay one step ahead of the people has he sworn his life to protect.
The Justice League investigates the arrival of a strange, purple glaive that now protrudes from the bustling streets of Central City. With even Superman unable to leave it due to its magical nature, the Man of Tomorrow acts in an uncharacteristically harsh manner before brusquely departing. As the Flash comments on how strangely Superman is acting, Wally notices that both his new boss Mister Terrific and his wife Linda Park are similarly curt with him as his day presumably resumes as normal. And in The Flash #775 by Jeremy Adams, Fernando Pasarin, Matt Ryan, Jeromy Cox and Steve Wands, the true extent of the glaive's sinister influence and source of its corrosive power is revealed to be Eclipso.
Created by Bob Haney and Lee Elias, Eclipso has been menacing the DC Universe since 1963's House of Secrets #61. With Eclipso's powers fueled by a magical black diamond that grows significantly stronger during an eclipse, Eclipso was revealed to be a demon of vengeance constantly on the search for a new host to unleash its fiendish will on the world as the primordial manifestation of the wrath of God. Eclipso has bonded to many familiar hosts over the course of its history, with the original comic book host Bruce Gordon appearing as a new major antagonist in Stargirl Season 2 that battled the Justice Society of America before attempting to corrupt a new generation of superheroes.
Apart from corrupting the people of Central City, including Terrific, Eclipso's glaive also serves as a makeshift beacon to lure numerous supervillains to Central City for its alluring power. Running the risk of being overwhelmed and with all of Central City violently running wild on the streets, Wally obtains a portable forcefield and attempts to contain the glaive's emanating energy from continuing to corrupt those nearby. This plan, however, backfires, when the forcefield is overloaded by the sheer amount of negative energy building up inside, unleashing it on the city and effectively making the entire situation visibly worse as the Flash realizes he will need some magical help to save the day.
Eclipso has been a threat worthy of the entire DC superhero community's attention on multiple occasions and the Flash has found his whole hometown caught in the magical supervillain's corrosive thrall. While Wally is able to stay one step ahead of all those corrupted by Eclipso's power so far and ultimately managed to drive the villain out of Central City, the showdown definitely left a mark on the city. And with Eclipso still on the loose, no one in the DCU is safe as long as Eclipso continues to evade justice.