A collection of various supervillains originally assembled to Baron Heinrich Zemo to aid him in defeating Captain America and The Avengers (Avengers #6). Featuring an ever changing roster of most dangerous supervillains. After their original plot failed all the Masters except Zemo were captured, Baron Zemo again attempted to defeat The Avengers with new members Enchantress and Executioner. All three members were trapped in a Space Warp by Thor, while trying to escape (Avengers #7).
Eventually The Masters manage to escape the warp thanks to Enchantress’ magic. Upon returning, Baron Zemo transformers Simon Williams into Wonder Man, only to have him turn on The Masters in their moment of triumph (Avengers#9).
Later, The Masters are approached by Immortus, Ruler of Limbo. Immortus offers to help The Masters defeat The Avengers because doing so also furthers his goals. While Immortus has Captain America trapped in the past, The Masters of Evil near defeat The Avengers, and only the timely return of Captain America prevents them from doing so. In the end, Enchantress must send The Masters back in time to prevent their most recent defeat (Avengers #10).
The Masters are left leaderless after Baron Zemo is killed in an avalanche during yet another attempt to defeat The Avengers (Avengers #15).