A sort of creepy, evil would-be telepathic Batman from another reality. This is the 1964 version, not the Grant Morrison one. Best read after the Ages of DC Comics and the “base camp” profile for the pre-Crisis Earth-3 Crime Syndicate of America.
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This is the original version of the evil Justice League from Earth-3. So, the 1964-1985 take on the concept. “Base camp” article that explains all the things that would be redundant in these guys’ individual profiles. Best read after our guide to the ages and Earths of DC Comics.