Enigma actually sampled quite a bit of the album for their seminal work, MCMXC a.D., and listening to 666 for the first time, having been quite a fan of Enigma was very revealing. I knew that they sampled heavily (oh, those halcyon days) from many different sources, but it's always fun to hear something you know in a different way.
The famous heavy breathing from Enigma's Principles of Lust, for instance, is a sample from "∞", a five minute song supposedly cut down from 39 minutes, recorded in a single take, where Greek actress Irene Papas chants, "I was, I am, I am to come" over and over, in increasingly hysterical tones.
Anyway, it's some pretty heavy progressive rock, with seriously apocalyptic overtones. So enjoy!