The Captain Atom Brigade was a team assembled briefly by Breach as a suppously attempt to create a force capable to stop the Monarch, by then a corrupted version of Captain Atom.
However it was revealed than Breach was under Monarch control and the attack of the Brigade was something planed. When the team attacked, Monarch killed and absorbed most of their members, including Breach to increase his own powerbeore attack the Monitors forces.
After the explosion than almost destroyed earth-51, (but instead reboot it), Monarch was throw away and restored back to his Captain Atom form, who awake as prisioner of Project 7734 is plausible believe than the alternate Captain Atoms were restored to their proper worlds. However, if they stay the same as their previos form is questionable.
Is unclear which events of Arena still are canon after Flashpoint, because several earths are not the same as in the Countdown: Arena limited.
Among the most reconogzible members of the Brigade it can be included:
- Breach: From earth-0, also posible from pre-COIE earth-8.
- Captain Atom: The original inspired character from Charlton Comics. Possible from earth-4, pre-COIE.
- Quantum Storm: Mash-up of Firestorm and Captain Atom. From Earth-37, pre-Flashpoint.
- Captain Adama: Female version. Possible earth-11.
- Quantum Boy: Teenage version. Unknown earth.
- Atum: A Hulk like Atom. Unknown earth.
- President Adam: Includes an Atomic Shield resembling Captain America. Unknown earth.
- Quantum Mechanic: A cybernetic Giant. Possible from earth-44.
- Dr. Manhattan: A look-a-like member similar to Watchmen's Dr. Manhattan.
- Kid Quantum: James Cullen, from the Legion of Superheroes. Unknown earth, posible earth-264, Zero Hour Legion.
- Captain Atom and the Atomic Knights: From pre-Flashpoint earth-38.
- Comrade Atom: From earth-30, subaltern to Red Son Superman.
- Brigadier Atom: From earth-13, husband of Eve of Shadows.
- Kingdom Come Captain Atom: From earth-22.
- Unknown Atomic Monarch: A heroic version of Monarch, with atomic powers. Unknown earth.
Post Flaspoint, the existence of many of this characteres is not considered cannon. Yet is possible than a lot of them has survived the Flashpoint reboot.