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Korvac first appears in Giant-Size Defenders #3 (1975) as a pawn of the cosmic entity the Grandmaster. According to Gerber:
“ The character really was a throwaway, created for one story. And I never intended to bring him back, because, among other things, I hated the name! I still think it sounds more like a vacuum cleaner than a villain. [1] ”
While the story maintains that it is in fact the 31st century, it is established years later that this timeline is in fact the future of the alternate dimension Earth-691. [2]
In 1977, Korvac reappears in Thor Annual #6, written by Roger Stern and art by Sal Buscema. This story acts as a prelude to the "Korvac Saga", which was published in Avengers #167 - 177 (Jan. - Nov 1978). The story arc was written by Jim Shooter and David Michelinie, with art by George Pérez and David Wenzel.