Zardoz (1973)

The distant future: while the savage Brutals rule the wastelands, worshipping the flying stone head Zardoz, the Eternals, a ruling elite, live in a pastoral enclave. But their idyll is ruined by a plague that is decimating their numbers, leaving the Eternals lethargic and virtually catatonic. One of the Brutals, the Exterminator Zed, infiltrates the Eternal enclave and, in an abandoned library, discovers the truth behind Zardoz and threatens to disrupt the balance of power… […]