This is all pretty subjective because one person may have one type of a feeling about this extract, and the other person may have completely different feelings.
For me personally, this simile creates a gloomy mood. The simile 'the hollow halo it was in was like an icy crystal cup' creates a gloomy and cold atmosphere in my opinion.
When you preview something, you inspect it. Previewing helps you get a glimpse of what's ahead before you read or something, kind of like skimming.
To me , this means that the scene changed very quickly into something that is more meaningful and intriguing
The inflection of the verb occurred is a past-tense.
