Kothar and the Wizard Slayer — Gardner Francis Fox

THE DEATH OF MAGIC
Someone - or something - was systematically killing all the world's magicians. Kothar, the blond barbarian, had to link up with his enemy, the she-devil temptress Red Lori, to find and vanquish the slayer. Beautiful Lori was his partner but Kothar's best friend was still his magic sword Frostfire.

Wizard's Revenge . . .
A great hand - a thing of stone and rock, hideously carved and with strange spells and incantations limned on its rock surface - reached in the opening it had made, and stabbed forward. Blunt fingers closed around the squirming, screaming necromancer.
"Dread Omorphon! Awful being of the nether hells - aid me!
He tried to fight it, but his hands could do nothing against the solid rock out of which that other hand was formed. The fingers tightened, and now the magician began to swell curiously at chest and legs, as if other parts of his body were being forced into them by that frightful grip. His face became purple with congested blood. His eyes bulged hideously. A trickle of blood ran from his open mouth.