Heck was the artist co-creator of several new characters in the "Iron Man" feature. The Mandarin debuted in "Tales of Suspense" #50 (Feb. 1964) and would become one of Iron Man's major enemies. Hawkeye, Marvel's archer supreme, first appeared in "Tales of Suspense" #57 (Sept. 1964), following the introduction of "femme fatale" Communist spy and future superheroine and S.H.I.E.L.D. agent the Black Widow in #52 (April 1964). He drew the feature "Iron Man" through issue #46 (Oct. 1963), after which Spider-Man artist Steve Ditko introduced the familiar red-and-gold Iron Man armor and drew three issues. Heck returned with #50 and continued through #72 (Dec. 1965).