I expect thrax is more a magical offspring rather than The result of sex between Rita and zedd

Also I would like to see the continuing adventures of zenaku and Merrick

That's the only thing that could probably make sense about Thrax...but the thought of Zedd and Rita "doing it"...oh God. My theory on Thrax? Lord Zedd probably already had him before he and Rita got hitched, and in the event that Zedd was ever destroyed, his son would take his place, perhaps as a contingency plan of sorts. Why else does he have his dad's Z-Staff?