- "The JSA are basically a group of super-soldiers. To win, the Reich will need their own. This is just a taste. Enough to dose one person. Proof of concept. Give me what I want and your Führer will be planting his flag on the White House lawn within a matter of months."
- —Eobard Thawne presenting the enhancer to Baron Krieger[src]
The biomolecular enhancer (mistakenly dubbed "the serum" and "super-serum" by Krieger) was presented by the time-traveling meta-human Eobard Thawne to Nazi authorities in 1942, as proof of his alliance with Nazi Germany, and as a bargaining chip for Eobard to get a specific item from Adolf Hitler. The enhancer was used by Baron Krieger to mutate into der Übermensch, and later to heal the heavy wounds of Nate Heywood, who suffered from hemophilia. A side effect of the enhancer turned Nate into a meta-human under the alias "Steel".
The biomolecular enhancer allowed to modify a normal human being on a molecular level, mutating them into a meta-human creature of enormous size, strength and resilience, while also affecting their ability to speak, turning the mutated into a "berserker". A version modified by Ray Palmer also allowed to cure hemophilia, although it still contained the original's mutative reagents and affected its user. The version modified by Ray also ended up allowing Nate Heywood to mutate at will into his meta-human form that he introduced as "Steel". Both Krieger and Heywood could not stay in their meta-human forms indefinitely, struggling to keep their powers, or, in Krieger's case, using the enhancer multiple times.
At some point in time, Eobard Thawne created the biomolecular enhancer that allowed to modify a normal human being on a molecular level, mutating them into a meta-human creature of enormous size, strength and resilience. In 1942, Thawne visited the lands controlled by Nazi Germany, specifically Paris, France, to discuss a deal with Baron Krieger, a SS-Standartenführer. Eobard asked Krieger about the location of a certain item that the time-traveler sought, to which Krieger replied that the item of interest was located in Berlin, but Adolf Hitler refused to part with it. To convince the Führer, Eobard presented Krieger with a sample of his biomolecular enhancer, saying that the Nazis will need it to even the field with the United States (Earth One)' Justice Society of America, a group that included meta-humans and other extraordinary beings. Thawne promised to give the Nazis more of his enhancer if Hitler agreed to give him the item he seeks.
Deciding to test the serum, Krieger transformed into a mutated being that he later dubbed "der Übermensch" to combat Ray Palmer and Amaya Jiwe, successfully defeating the two, while his soldiers captured them. Krieger then found himself reversing back to his human form and interrogated the prisoners, boasting of his newfound might. Trying to bargain for time, Ray Palmer said that one "roid rage" wasn't enough and suggested to help Krieger produce more of the "serum", allowing him to go back on the deal with Thawne completely. Krieger agreed and left Palmer to his devices. Modifying the sample of the enhancer, Palmer waited for the Nazi to leave before escaping along with Amaya.
Alerted, Krieger used the enhancer to transform into the "Super-Krieger" once more and pursued Justice Society and the Legends, but was destroyed in the process of a bombing run. The bombs also damaged a motorbike used by Henry Heywood and Nate Heywood, leaving the latter heavily damaged and nearly dead, his state worsened by hemophilia. Back on the Waverider, Ray Palmer thought to use the modified version of the enhancer he created in Krieger's HQ on Nate Heywood to heal his wounds, succeeding, and also affecting Nate with the "super-serum's" effects.
The effect became evident later, when the Legends had witnessed Nate's transformation into a meta-human form with metallic appearance and adjacent strength, able to resist every shot and punch from Ray Palmer's A.T.O.M. Exosuit. Like Krieger, Nate couldn't keep his meta-human form indefinitely, but instead of repeatedly using the biomolecular enhancer, he had to focus and release his power at the times of great peril, mastering his power to defeat Tokugawa Iemitsu.
DC's Legends of Tomorrow
- When Baron Krieger called this drug "the serum" (referencing the typical name of "super-soldier serums" used in pulp fiction based on military history), Ray Palmer corrected him, saying that the term "serum" would be incorrect in this case, as the drug is a mutative biomolecular enhancer. Despite correcting Krieger, Ray continued to use the term "serum" later, for convenience, explaining the drug to Nate Heywood.