|First appearance||Showcase #39 (July–Aug. 1962)|
|Created by||Robert Kanigher|
|Team affiliations||Injustice League|
|Abilities||Superhuman strength and durability|
Expelling hazardous liquid materials
Chemo debuted in a story called "The Deathless Doom" in Showcase #39 - 40 (July - Aug & Sept. - Oct. 1962), being the adversary for DC Comics' new superteam the Metal Men. The character returned in Metal Men #14 (July 1965); #25 (May 1967) and #46 - 47 (July & Sept. 1976).
The character was reimagined in Supergirl vol. 4, #5 (Jan. 1997) and then appeared briefly during the Our Worlds At War storyline in Adventures of Superman #593 - 594 (Aug. - Sept. 2001) and in Birds of Prey #36 (Dec. 2001) and Joker: Last Laugh #2 (Dec. 2001).
Chemo featured as a major villain in the limited series Infinite Crisis #1 - 7 (Dec. 2005 - June 2006) and appeared in multiple forms in Superman #663 (July 2007). The character also appeared in Outsiders - Five of a Kind: Nightwing/Captain Boomerang (Oct. 2007); Salvation Run #1 - 7 (Nov. 2007 – June 2008) and in Booster Gold vol. 2, #13 (Dec. 2008).
Writer Mike Conroy noted "where would comic books be without those flukes, those accidents of fate which, although inexplicable to science, result in innocuous materials having a far-reaching impact on the world outside the laboratory?"
Chemo was originally the nickname given to a plastic vessel used by scientist Ramsey Norton to contain the chemical by-products from his failed experiments. When Norton places the remnants of a failed growth formula in the vessel as his latest contribution, it accidentally brings the man-shaped vessel to life as "Chemo". After killing Norton, Chemo goes on a rampage until stopped by Will Magnus' robot team, the Metal Men. Chemo regenerates and returns, but is defeated each time by the Metal Men.
During the Crisis on Infinite Earths, villains Brainiac and Lex Luthor use Chemo as a living weapon on Earth-4. Chemo destroys the alternate universe version of New York City and kills Aquagirl by releasing large quantities of toxic chemicals into the ocean. The entity is dispersed and neutralized when the heroine Negative Woman shatters Chemo's plastic shell.
During the Infinite Crisis storyline, Alexander Luthor Jr.'s incarnation of the Secret Society of Super Villains employs the Brotherhood of Evil to use Chemo as a living weapon by dropping the entity onto the city of Blüdhaven. At the same time in the "Batman: Under the Hood" storyline, Batman sees Chemo hit Blüdhaven from a rooftop in Gotham City. After Chemo covers the city with toxic waste, Chemo kills hundreds of thousands of people, but is stopped when Superman throws the entity into deep space.
During the Salvation Run storyline, Chemo is retrieved and used as a weapon by fellow villains the Joker and Gorilla Grodd whilst on a prison planet. Rogue New Gods visiting the city of Metropolis capture a trio of multicolored miniature versions of Chemo. Superman follows the true Chemo and discovers it to be a LexCorp project.
In September 2011, The New 52 rebooted DC's continuity. In this new timeline, during the "Forever Evil" storyline, a flashback sequence reveals that Chemo is created when a prototype responsometer created by Will Magnus is thrown into a vat of chemicals by a thief. The Metal Men battle Chemo to protect Will Magnus and the local population, and while successful were apparently also destroyed.
The character is written as having very limited intelligence, superhuman strength and durability and is capable of altering its mass and projecting hazardous chemicals.
Chemo appears in the direct-to-video animated film Batman Unlimited: Mech vs. Mutants (2016), voiced by Dave B. Mitchell.
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