The Brain was a former French scientist whose body had expired had his brain transplanted into a sophisticated receptacle connected to a large computer network. This procedure was performed by his assistant, Monsieur Mallah, who had himself formerly been an ape that was granted vast intellect by his master's treatments. Together, they formed the Brotherhood of Evil, including in their ranks former actress Laura DeMille who had been involved in an accident, now transformed into the appearance-changing Madame Rogue.
While there was a Monster Society of Evil on Earth-Two that paralleled the Brain's Brotherhood, even with it's own malevolent mastermind behind it in the alien Mister Mind who assembled it, it was in fact another crooked cranium who was the the counterpart of the Brain and Mallah, that being industrialists Jason Rogers who had a twin that never developed a body. This disembodied brain willed Jason's body into becoming the beast-like Monster.
Along the way, other super villains such as Garguax and General Immortus joined the Brotherhood for a time, on each occasion battling and facing defeat versus the Doom Patrol. The counterparts on Earth-Two of Garguax and his alien masters were a similar set of alien gamesman who abducted several star athletes including the golden age Flash, who ended up defeating them which forced them to return their captives to Earth-Two.
Other recruits in the Monster Society were Ramulus and Nyola as well as the willful stone brute known as Oom, which made this evil assemblage a true threat to the All-Star Squadron.
After a number of encounters, the Brotherhood fractured as Rogue rebelled against both the Brotherhood's Brain who was her master and the Patrol's Chief whom she loved, seemingly destroying both groups. The Monster Society had fractured leadership wherein its first leader Mister Mind left that Earth for another, then its second leader Oom was destroyed. While never joining the Monster Society even though it had the same name as the villain himself, the Monster was recruited by time tyrant Per Degaton into a group of supervillains who battled the All-Star Squadron in the early 1940's. Both Madame Rogue and the heroic Madame Fatale of Earth-Two likewise shared similar attributes as they could convincingly change their appearances, and had the same number of adventures..
Back on Earth-One, the Brain assembled a second team of villains from around the world to compose his new Brotherhood of Evil, this time battling the New Teen Titans and their ally Robotman. Meanwhile, the original Psycho-Pirate enlisted fellow cellmate Roger Hayden to become his protegee in foul play on Earth-Two with Hayden dueling with Hourman and Doctor Fate.
As a result, two teams of a sort were formed to torment the heroes of their worlds. First, there was the mentally manipulating Mango the Mighty and Houngan aka Jean Louis-Droo who used science to control men. Phobia (Angela Hawkins) and Psycho-Pirate II both used their abilities to effect other humans' emotions. This pair also worked with dimensional traveling Warp and Mayoor, which cause their foes to phase out of reality. Pirate later solicited the services of former crime boss Gat Benson, transformed by green plasma into a gigantic beast much like that of the Brotherhood's Plasmus, who used to be Otto Von Furth until his physiology had been altered due to exposure to radioactive radium.
While the Brotherhood of Evil invaded the African country of Zandia and later resurfaced in America, never finding success in the schemes of their leader. Psycho-Pirate struck off on his own after his previous allies Wotan, Mayoor and Benson had failed him, controlling a team of Justice Society members Green Lantern, Flash and Batman until the trio were defeated as was their puppet-master by the rest of the team. The Pirate then allied himself with the Secret Society of Super-Villains until the Crisis when he became the Anti-Monitors right-hand henchmen for a brief time.