Philip Jose Farmer 
Behind the Walls of Terra 

Behind the walls of Terra lay a secret no man could be allowed to learn. But Kickaha – the Earth-born adventurer of the tiered worlds – had to uncover that secret, or watch his home world destroyed.Kickaha was returning to Earth from the World of Tiers, the many-levelled universe of the god-like Lords, that he had entered many years ago as Paul Janus Finnegan. Now he had returned to a world he no longer knew, to find it ruled by Red Orc, a Lord jealous of his personal domain and hostile to intruders. Yet Kickaha had to stay alive in order to defeat the deadly enemy that threatened Earth and the other worlds of tiers – the 'Beller’, the malignant creature that was the mind-essence of a rebel Lord.