Neil Charles & Denis Hughes 
Beyond Zoaster [EPUB ebook] 

When Zaan, the ruler of the dying world of Ginya, set his sights on Earth as a place where his race could prosper and be safe from extinction, conquest was assured. The people of Earth were decadent and sunk in idle complacency and peace and technological advancement came to the world when the Ginyan race became Earth’s overlords. Only a small group of human beings saw far enough ahead to exile themselves on dark Zoaster with a view to freeing the world from alien rule in the future, hoping to build up an army of synthetic supermen who would one day sweep the Ginyan race from the face of the Earth. They did not count on the weird elementals that dwelt on Zoaster, spirits of evil and darkness . . .