pre-Crisis
Quex-Ul was sentenced to the Phantom Zone for killing Rondors on Krypton. Quex-Ul was released from the Phantom Zone by Superman when his sentence was complete. Quex-Ul lost his super-powers and his memory by saving Superman from a Gold Kryptonite trap. As a mortal, Quex-Ul took the name Charlie Kweskill. He worked for the Daily Planet as a production artist.
Post-Crisis
Quex-Ul was a Phantom Zone inhabitant. He was seen with other inhabitants of the Phantom Zone, including General Zod, Jax-Ur, Non, Ursa, Car-Vex, Az-Rel, and Nadria.
He is later killed by Squad K of Project 7734.
A pocket Universe version of Quex-Ul was killed by Green Kryptonite when Superman used it on him when he, General Zod, and Zoara destroyed the pocket Earth.