Secret of the Sixth Magic — Lyndon Hardy

BEYOND THE FIVE MAGICS

The laws of the five magics were being set aside. First to go were those of the high art of sorcery. Then true magic, upon which the commerce of all Arcadia depended, had been voided. And now even thaumaturgy, the engineering knowledge of the world, was under attack.

Jemidon had traced the trouble to Melizar, the strange, cold being who had seemingly appeared from nowhere. Somehow, Melizar could alter or negate the laws that had always existed by using a mysterious metamagic--something which only he understood.

If the world was to be saved from Melizar, it was up to Jemidon to save it. But what could he do? He was only an outcast, unable to perform even the simplest ritual without ruining everything.