Meanwhile, Dark Nights: Metal, written by Scott Snyder, introduced the concept of the Dark Multiverse, a multiverse below the main DC Multiverse of nightmare worlds created from heroes' deepest fears. A being named Barbatos launches an attack from the Dark Multiverse on reality, spearheaded by a force of villainous versions of Batman lead by The Batman Who Laughs. The invasion is defeated, but the Source Wall at the boundary of the Multiverse is cracked and the Batman Who Laughs manages to escape into the main DC Universe. The story is continued in Justice League. In Snyder's run on Justice League, the crack in the Source Wall allows the Totality, a small meteorite bearing immense power, to enter the Multiverse from the Source beyond. Lex Luthor retrieves the Totality and eventually frees Perpetua, the creator of the Multiverse. Despite the heroes' best efforts they are ultimately defeated. At the end of Justice League #39, the defeated League are saved from destruction by the Quintessence, who grant them the power necessary to fight Perpetua. The team run into a portal for the final battle, but this conflict is not shown and from there Justice League follows the team on other adventures, written by new writers. In the special event comic Year of the Villain: Hell Arisen, the Batman Who Laughs joins with Perpetua. The resolution to the Perpetua story arc was advertised in Justice League #39 as "The Encore", which would eventually be published as Dark Nights: Death Metal. Published roughly contemporaneously, a six-issue miniseries titled Flash Forward follows Wally West being enlisted by a cosmic being known as Tempus Fuginaut to stop an incursion of the Dark Multiverse. At the end of the series, Wally sits in the Mobius Chair, gaining omniscience and residual power from Dr. Manhattan. In an epilogue published in The Flash #750, Wally surveys the timestream and notices multiple contradictions and inconsistencies within history, the result of Manhattan's reckless tampering with time. This was originally intended to lead into the Generations miniseries and a reboot of the Multiverse termed "5G", which would have fixed all of DC's publishing history into a single coherent continuity, stretching from World War II to the present day, with stories going forward focussing on new characters or aged versions of current ones. "A Brave New World", intended to be the first story set in this continuity, was published in Wonder Woman #750.