As a young boy, Lou Dexter first discovered his mutant powers when he inadvertently mimicked his dead cat. He later developed more of an understand of his power a few years later when he returned home to find his father dead and upon touching his lifeless body became an identical facsimile of his father. Becoming obsessed with his own powers, Dexter began practising using his powers and delaying the transformation by attending random funerals of people he didn't know. Wanting more from his power, Dexter began studying superhuman obituaries and began exhuming their graves and serving a finger from their bodies which he would keep in a cigar box so he could transform into that person and have their powers whenever necessary.
Dexter was eventually caught while attempting to rob a grave and sent to prison where he was cell-mates with a member of the Watchdogs known as Mike Farrell who had grown to despise Captain America for having ruined his life. The two decided to team up to destroy Captain America's reputation, Farrell out of revenge, and Dexter out of ambition to claim a sample of Captain America's dead body and become an "a-lister".
Dead Ringer was created by Mark Gruenwald and Dave Hoover and first appeared in Captain America #425.
Dead Ringer first appeared in the beginning of Mark Gruenwald's final Captain America saga Fighting Chance which ran from issues #425-443. Dead Ringer appeared in several issues as a featured villain and was eventually defeated in #439. Since then Dead Ringer has not reappeared, a strong suggestion for his lack of reappearance is because Marvel do not want to address the fact that almost all of the superhumans he had transformed into have since been revealed as not dead or brought back to life. Dead Ringer was featured in Captain America: America's Avenger where his powers were radically altered to include being able to mimic appearance and powers from dead skin cells in order to slightly explain away some of the continuity problems.
Major Story Arcs
Dead Ringer and Mike Farrell, now outfitted as the Super-Patriot, began a smear campaign against Captain America. Dead Ringer would pose as a dead super-villain and Farrell would dress up as Captain America and incompetently "fight" Dead Ringer causing as much collateral damage as possible. At the same time, the duo would work to make Super-Patriot seem better than Captain America.
The two of them launched on attack on Captain America and the Avengers, with Dead Ringer taking the form of Mirage and using his powers to make it appear that the original Masters of Evil were attacking Avengers Mansion. With Captain America being the only one to see the mirage, his team-mates and the public believed he was going insane. Subsequently, Super-Patriot exposed the real culprit making Captain America look inferior by comparison. Despite Dead Ringer and Super-Patriot making progress with their campaign, Captain America managed to deduce that Super-Patriot was also the person impersonating him and attempting to make him look useless.
When Dead Ringer and Super-Patriot took Bernie Rosenthal and Diamondback hostage, they were defeated by Captain America and Quicksilver. While Dead Ringer was caught, Super-Patriot managed to escape, although Captain America managed to prove that he was the one pretending to be him when Super-Patriot accidentally forgot to hide his replica of Captain America's shield.
Eventually, Dead Ringer escaped captivity and he and Super-Patriot began to plot revenge against Captain America. When confronted by Captain America again, Dead Ringer mimicked the powers of Death-Stalker and in the ensuing fight accidentally touched Super-Patriot and killed him.
Powers and Abilities
Dead Ringer's mutant power is the ability to mimic any dead person he comes into contact with. His mimicry copies that person's appearance, clothes and any superhuman powers. However, Dead Ringer is limited in that he can only transform into a person once upon contact with a part of their corpse. He cannot "store" identities for use more than once, although if he touches their corpse again he can become them again. In response to this, he collects samples of the super-powered dead people he wishes to become more than once and these samples in a cigar box he carries on him at all times.
Among those Dead Ringer has at his disposal include Basilisk, Blackout, Blue Streak, Cheetah, Death-Stalker, Death Adder, Mirage, Night Flyer, Nighthawk, Porcupine, Purple Man, Snapdragon and Solarr. While impersonating these superhumans he has all of their powers and abilities, and in most cases also acquires their battle armors and weapons upon transforming into them. The extent of scientific duplication of these things is unknown but they still appear to function as the real deal. They also disappear when Dead Ringer transforms back into himself.
Dead Ringer's power was retconned, quite heavily, in order to explain how he was able to become characters such as Blackout, Nighthawk and Purple Man - all of whom were revealed to not have been dead afterwards. His mimicry is no longer limited to just dead people, but dead skin cells of living people too. Whether he is aware of this is unknown.