The Heritage of Hastur

From back cover of Daw paperback August 1975:

THE EPIC of DARKOVER

Described as "Bradley's best novel" by Locus, THE HERITAGE OF HASTUR, longest and most intricate of the Darkover books, is a brilliant epic of the pivotal event in the strange love-hate relationship between the Terran worlds and the semi-alien offspring of forgotten peoples.

This is a novel of the Hastur tradition and of the showdown between those who would bargain away their world for the glories of star-borne science and those who would preserve the special "matrix" power that was at once the prize and the burden of ruddy-sunned Darkover.