The Near-Apocalypse of '09 was a dramatic, near-cataclysmic event in the DCAU, first mentioned in the Batman Beyond episode "Out of the Past," in which Batman and Talia Al Ghul played critical roles in the heroes' ultimate success. Details are vague with no real explicit information available, either in-episode or from DCAU creators. Only a few particulars were dropped in-episode to provide a general breakdown of the event.
Batman, Ra's Al Ghul and Talia Al Ghul were key players in the conflict, and while overall details on said conflict are largely unknown, there are a few small facts available. According to details picked up from Batman Beyond "Out of the Past" and Justice League Unlimited "Epilogue," Talia turned on her father and aided Batman in putting an end to Ra's apocalyptic plot. While exact machinations are unknown, it's assumed the plot follows Ra's standard M.O.
Additionally, it was thought Ra's perished during the climactic battle of the Near-Apocalypse of '09, but that would eventually be proven wrong. Ra's was severely injured during event, far beyond what the Lazarus Pit could restore. To save him, Talia sacrificed her life and body. Ra's' neural patterns were transferred into her, with Ra's effectively reborn in his own daughter's body. It is unknown if Talia's sacrifice was consentual or forced. From there, Ra's laid low to plot his eventual return.
No other details on the events are known.
The Near-Apocalypse of '09
Discussion: Is "The Near Apocalypse of '09" something even you think they should show?