I will like it plugin that will add smoke that moves around and there will be strange noises when they go by you.
Apex Da_Pepsi_Monster is right, very possible indeed, loads of ways to do this, invisible mob, just a place in the world that gets changed etc
VariableTriggers seems that will be great for my haunted house and maze I am making for the server. I am wondering tho how will I make the smoke move around ???????