Well, what do all good little demons do when they get to run free through the tulips of the mortal realm? .... Devour souls of course, because they're so tasty. Seeing how easy it is to manipulate the mortals is also fun, especially when they kill each other over silly little things. Torture, especially any mental torture is also yum, like rape, then making sure they know that you're watching. Little things like that. You want it to end? Why? It doesn't have to have some neat little conclusion, they could just stay like that, none would be the wiser, especially since the vessels just look like little kids.