So, playing on a server running direwolf20, I want to fire off a demon invasion. Now I know that lots of players prefer to create a demon invasion in a mystcraft or RF Tools dimension, but I prefer to build (and destroy) the overworld. Theres quite a lot of it And, I would like the demon invasion to continue to grow when I am not there - it grows (apparently) up to 1000m x 1000m. So, given that my base is already underground, I was wondering if the Demon Invasion, triggered on the surface, would negatively effect my underground facility. In a demon invasion what spawns the demons - do they spawn in the surface structures or can they spawn at any y-level in occupied territory? Can the invasion structures appear underground and destroy my things? Or are they confined to the surface?