Brainiac 5 is a green-skinned, blond-haired teenager, dressed in a purple jumpsuit, who
claimed to be descended from the original Brainiac, one of Superman's deadliest enemies.
He wished to join the Legion as atonement for his great-great-grandfather's misdeeds.
Brainiac I was revealed to be an android created by the Computer Tyrants, Brainiac 5
"discovered" he was actually descended from Brainiac ii, the leader of the rebellion against the tyrants, as well as being the clone of the original Brainiac. Brainiac 5's ingenuity led to the invention of, amongst other things, the Legion flight ring the anti-lead serum that allowed Mon-El to leave the Phantom Zone and the force field belt which became the signature device of the character. Another of Brainiac 5's creations would have less beneficial effects.
The super computer Computo, which he created, attempted to take over the world, killing one of Triplicate Girl's three selves. He successfully destroyed his creation with "anti-matter force", but this highlighted one of his major flaws: a habit of initiating projects without considering the dangers. In fact, as time went on, Brainiac 5 began to be portrayed as unstable. Long attracted to Supergirl, Brainiac 5 created a robot duplicate of her in his sleep, convincing himself this was the real Supergirl. He seemed to recover from this, but a few years later would become even more unbalanced. The Legion later encountered Pulsar Stargrave, a villain who convinced Brainiac 5 that he was the Coluan's long-lost father. Brainiac 5 joined Stargrave to battle the sorcerer Mordru, but the android's influence would haunt him long after that.
When Stargrave murdered Ultra Boy's ex-girlfriend An Ryd, Brainiac 5, driven mad by Stargrave, framed Ultra Boy for the murder. Chameleon Boy, who suspected this from the beginning, finally found proof when Brainiac's madness led him to an attempt to destroy the universe, utilizing the Miracle Machine, a device that turned thoughts into reality.
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For more information on Brainiac 5 DC DATABASE
MAJOR SPOILERS - pages from the issues
THE BRONZE ERA - the issues