The Squadron Sinister is a fictional supervillain team that appears in comic books published by Marvel Comics. The Squadron Sinister first appeared in the final panel of The Avengers #69 (Oct. 1969) and were created by Roy Thomas and Sal Buscema.
The first version of the Squadron Sinister is formed by Elder of the Universe and the Grandmaster as pawns to battle the champions of the time-traveling Kang the Conqueror, the superhero team the Avengers. The Grandmaster creates four villains — Doctor Spectrum; Hyperion; Nighthawk and the Whizzer — to face heroes Iron Man, Thor, Captain America and Goliath (Clint Barton). In interviews, Thomas and Jerry Bails have stated that the Squadron was based on the DC Comics superhero team the Justice League of America.
The limited series Squadron Supreme, written by Mark Gruenwald, explains that the Grandmaster creates the Squadron Sinister modeled on the already-existing Squadron Supreme of the Earth-712 universe. The similarities also cause confusion in Marvel's production department, as the covers of The Avengers #85 (Feb. 1971) and #141 (Nov. 1975) "cover-blurbed" appearances by the Squadron Sinister, when in fact it was the Squadron Supreme that appeared in both issues.