I have it from Jake (haven’t seen the film myself) that this is the synopsis of the film.
In the future, the world is separated into two camps: the civilized people who live in a protected bubble enjoying art and pleasure and the savages living outside the bubble. The bubble people control the savages by sending them a giant head called Zardoz that they worship. Zardoz also gives the people guns. One of the savages of the Exterminator class played by Sean Connery hides inside Zardoz’s head. The head returns to the bubble where Sean Connery completely undoes the bubble civilization.