Sadly it's in German, but I've been reliably informed of the crucial relevance of the moon, butterflies, owls, geckos, & mirrors in spiritistic practices - all featured in the "slave's" offering! Perhaps someone with a knowledge of German can provide a more detailed analysis.
According to this guy's forensic examination of the video, it uses spiritistic practices and symbolism repeatedly. Far too much to be a coincidence?
The use of chiming bells is also used in spiritism, and by playing the soundtrack backwards, he highlights what has been done in the past by various pop groups including The Beatles.