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The Thunderbolts were first presented, both to readers and to the Marvel Universe, as a group of super-powered figures who became heroes to help protect the world when the Avengers were declared dead after the events of the 1996 "Onslaught" crossover. The final page of the first issue of their comic book, however, revealed that the Thunderbolts were actually the Masters of Evil in disguise, a surprise twist carefully guarded by Marvel. 

Themes of redemption and the nature of heroism are often featured in Thunderbolts comics.  The book has also garnered critical praise for its use of secondary characters from other Marvel Comics and its use of continuity-themed storytelling. 

The Thunderbolts was an original concept created for Marvel by Busiek and Bagley.  Most of the characters used in the final concept were reimagined versions of existing Marvel characters, with additional original characters for the series developed by Busiek and designed by Bagley.  The pair also created the new heroic identities for the Masters of Evil. Busiek recalled: 

“The actual origin of Thunderbolts came when I used to live in New Jersey and drive to New England to visit my parents. To keep myself awake, I'd give myself books to write, and work out about two to three years of continuity. One trip, I assigned myself Avengers, and came up with the plan that the Masters of Evil would ultimately conquer them by posing as new heroes and slowly replacing them. At the time, I thought it was a neat idea, and filed it away.”