Professor Va-Kox was once a great Kryptonian scientist. After contaminating the Great Krypton Lake with his life force formula, a lizard-like, multi-headed monster was born out of the lake. Due to this crime, he was banished to the Phantom Zone before Krypton was destroyed.
Vowing revenge for his imprisonment by threatening to unleash more monsters, Va-Kox waited in the Phantom Zone for the right time to escape. That time drew nearer as electrical ions of the Aurora Borealis created a hole in the Phantom Zone that led to Earth. Professor Va-Kox and other Phantom Zone prisoners waited for the hold between dimensions to become large enough for them to escape. Unfortunately for them, Superman, Supergirl, Mon-El, and Krypto became aware of the situation and used their combined X-ray vision to burn up the Aurora Borealis, which destroyed the link between the dimensions and closed the hole, foiling the escape attempt.