"Secret Weapon"
Triangle 1993-29.
Continued from Adventures of Superman (1987) #504, continues in Superman: The Man of Steel #26.
As Superman and Steel fight their way deeper into the heart of Engine City, Superboy falls from the sky after diverting a massive missile targeted for Metropolis.
In the Antarctic, the Eradicator siphons all of the Fortress power to hasten his healing process, obsessed with returning to Engine City for revenge against the Cyborg Superman.
As Superman and Steel draw closer to the control center of the enormous construct, Superman reveals that they are not alone and in fact have been accompanied by an invisible Supergirl the entire time.
While the cyborg's delusions and rantings grow worse Mongul decides it is time to end his alliance with the madman and prepares his ship for departure, but before he leaves he initiates a sequence that will ignite the massive Engine City and and throw Earth out of its orbit and the power source, a massive meteor of pure Kryptonite, will explode.