Jack Williamson 
Reign of Wizardry 

Before the Glory of Greece, Crete ruled the known world — and kept it enslaved by black magic! The evil of Minos held sway, protected by three unconquerable walls. First is the fleet that they call the wooden wall. Then there is a giant of living brass — he is the second wall. Then there is another barrier about the power of Minos, the Wall of Wizardry. Theseus, the tall Achean, the man they called Captain Firebrand, vowed to scale and destroy all three, and to rid the world of the evil yoke of Crete. But Minos had other defences besides the walls, and many ways to attack as well . . .