THE UNDERPEOPLE

Sphere SF paperback, 1975. Cover artist uncredited, possibly
Bruce Pennington or Ray Feibush.

"The Underpeople were mutated from animal stock to serve mankind. They lived downdeep in the forgotten corridors and caverns of old earth, servants to the men who bred them in their own image.

But even underpeople dream - and often have strange powers.

And now they have a strange ally in the richest man who ever lived: the man who owned the whole planet." 

This is my second copy of The Underpeople. I didn't intend on owning two different copies, but found this one in a box with about thirty other books.