WARNING: The following article contains spoilers for The Batman Who Laughs #1 by James Tynion IV and Riley Rossmo, on sale now.
As a disquieting amalgamation of Batman and his most notorious foe, The Joker, The Batman Who Laughs has arguably been the creepiest and most disturbing of the seven Dark Knights featured – at least so far – in Dark Nights: Metal. Having served as Barbatos' Dark Multiverse lieutenant and gathering the remaining nightmarish incarnations of Batman for their incursion into the known multiverse, the origin of the eeriest of these personifications is the final one to be told, courtesy of James Tynion IV and Riley Rossmo's The Batman Who Laughs #1.
Yes, as previously revealed by Scott Snyder in an interview with CBR, there is Joker toxin involved, but the issue shows that the character's beginnings have a much farther reach than just another encounter between two longstanding foes – beginnings that are drenched in the kind of darkness that readers have come to expect from any world in the Dark Multiverse.
The Joker's Last Laugh
That's not to say Batman and The Joker don't have a deadly encounter – in a decidedly high-stakes showdown along the same magnitude of Snyder and Greg Capullo's climactic "Endgame" arc in Batman, The Clown Prince of Earth -22 has Batman at his mercy as he launches a different kind of endgame. Having slain both the Gotham police force as well as the rest of Batman's foes, Joker embarks on a murder spree of Gotham's parents before proceeding to infect their orphaned children with his deadly toxin, engaging in a repeated perversion of Batman's own origin. When an enraged Batman breaks free, he commits an act atypical of the character in most worlds of the multiverse – whether intentionally or otherwise, he ends The Joker's killing spree by snapping the villain's neck during the course of their battle.
That's not the end of The Joker's impact on Batman's life, though, or on the rest of this world. Upon killing his foe in such close proximity, Batman is exposed to the very toxins that not only created The Joker in the first place, but continued to drive him into an increasingly downward spiral of insanity. These chemicals are shown to have the same adverse and slow-acting effects on Batman in the aftermath of The Joker's demise. Knowing that at some point that he will succumb to the nanotoxins and must be taken down, Batman establishes a rigid training protocol for Batgirl, Nightwing, Red Hood, and Red Robin to secretly prepare them for this eventual encounter. Upon revealing to them the reasons for this training, though, his mind snaps, and with The Joker's toxins now dominant, he fatally ambushes his four most trusted allies. Notably, Robin – aka his son Damian Wayne – is absent from this sequence.