You are nearing the end of the mid-hive levels and approaching the lower hive hence the buildings becoming less sturdy. Rainah you did not notice the cultists until now because their march is only now close enough for you to even see the banner. They are still a long ways off and have not seen you yet. 

Do not worry, in a post or two things will be getting very interesting very fast. If you read the post for Muse and Poly also you can probably note the very near future.