The Illearth War

From back cover Del Rey paperback September 1979:

WHILE THE EVIL DAYS COME

After scant days in his "real" world, Thomas Covenant found himself again summoned to the Land -- the strange world of magic and earthpower. There forty bitter years had passed while Lord Foul, immortal enemy of the Land, moved to fulfill his prophecy of doom. Foul's countless minions, led by a Giant Raver, were already on the march of destruction. They were opposed only by the untried war skill of Hile Troy, blind and bitter exile from "reality."

The Council of Lords found their spells useless, now that Foul the Despiser held the Illearth Stone, ancient source of evil power. High Lord Elena turned in desperation to Covenant and the legendary white gold magic of his ring. But Covenant was still the Unbeliever, unable to believe that the Land was more than illusion. And nobody knew how to use the white gold -- least of all, Thomas Covenant.