Mekanique comes from a future era that resembles Fritz Lang's film Metropolis, where a small elite ruled despotically over a downtrodden slave race. The elite were in danger of being overthrown due to a woman named Maria, who led the slaves into open rebellion. To combat this, an evil scientist named Rotwang created her and gave her the ability to travel back in time for the purpose of making sure Maria would never be born.
She arrived in 1942, appearing suddenly in the headquarters of the All-Star Squadron; badly damaged, Mekanique attacked Firebrand. Before she can be destroyed by Green Lantern, Robotman steps in and offered to repair her. A subsequent power surge threatened to destroy the headquarters, but instead restores Mekanique. She revealed that she is from the far future, and had returned to the past to prevent a horrible future war. Mekanique shows the heroes an image of a child about to be killed in a car accident, and they save her, thus changing the future. However, she reveals to Robotman secretly that the rescue of the child did not prevent the future war, but instead made certain that it took place. She also reveals that she had been holding back the "sweeping effects" of the Crisis On Infinite Earths from taking place until her mission has been fulfilled, and so causes the effects to take hold, blanking out Robotman's memory so that he cannot warn his fellow Squadron members.
Sometime after Johnny Chambers brought Helena Kosmatos to America, she starts having visions of a giant Mekanique attacking and massacring the entire All-Star Squadron. Soon afterward, Mekanique meets Per Degaton while he was still an assistant at the Time Trust. She convinced Degaton to help her in her fight against the All-Star Squadron, in exchange for teaching him the secrets of time travel. It is here where Helena's vision comes true in a different sense—Mekanique shrinks the entire All-Star Squadron minus the Young All-Stars to doll-size and attacks them in a model of a futuristic metropolis. However, with the help of the Young All-Stars, Robotman was able to activate a destruct mechanism that destroys Mekanique's body, leaving her head intact, thus restoring the All-Star Squadron members to normal size. Degaton managed to escape with Mekanique's head, and keeps it with him for the next five years, during which they fall in love.
By 1947, Degaton, Mekanique, and a new ally, Professor Malachi Zee, have managed to build a working time machine. Mekanique gave Degaton a crystal that would give power to the time machine to travel through time. Degaton, wanting the machine for himself, shoots Zee, who falls into the machine and accidentally sends it forty years into the future. Degaton lunged at the machine to prevent it from traveling to the future without him, but fails. When Mekanique suggests they wait forty years for the machine to reappear, Degaton snaps and buries Mekanique's head.
Forty years later, Degaton, now resigned to waiting for the time machine, reconstructed Mekanique. She appeared during the time of the Crisis On Infinite Earths in 1985 to manipulate Commander Steel into kidnapping and tampering with his grandson, who at the time became the Justice League hero known as Steel. As the Justice League teams together with the Justice Society and Infinity, Inc. to confront Mekanique in order to free the two heroes from her influence, she vanishes. She reappeared in Los Angeles a few years later to bring an aged Degaton who was struck by a car back to life, and the two of them attack Infinity, Inc. at the scheduled return site of the time machine. When the time machine appears, it contains not only the body of Zee, but a younger Degaton. This duplicate version of Degaton had been created by the chronal energies of the time machine as Degaton had lunged at the machine in 1947. The elder Degaton vanishes from existence at the appearance of his younger self, but fearing that the young Degaton would destroy her again, Mekanique activates a self-destruct that kills Degaton along with herself.