Re: "Caution: You are approaching the periphery shield of Vortex Four."
That seems like kind of a wordy warning if they're trying to repel Brutals. Whatever happened to Vortexes One through Three?
Zardoz came from the late 60s - early 70s age of "stream of random thought" SF, where even marginal internal consistency was secondary to "grooviness," and it was usually all about the inherent futility of all things. Small wonder Star Wars, despite its stark simplicity of plot, hit a starving audience like a truckload of grilled steaks.