Bio: Brainiac had one intent when he joined forces with Darkseid:
to lure Superman to him. Brainiac's conquering of Krypton wouldn't be
complete until its last survivor was killed--and Brainiac was going to
be one who destroyed him. However, Brainiac's plans were quickly put to
an end when he sent out his many duplications of himself. As each one
was destroyed, he only grew weaker. Presumably, Brainiac died in the
explosion that blew up his main headquarters, but knowing Brainiac, he
has duplicate copies of himself out there in the universe--it's only a
matter of time till they show up.
For more, refer to the Justice League Unlimited bio.