68608
I was meaning if inside a cave. =P Like, how you mentioned clearing out hollow hills; jetpack down, shoot one portal at the ceiling, place a torch, jetpack up, proceed to fire many portals under the mobs going to kill you, and watch as they fall to their deaths. =P
Truth: Nice. =P
68613
Because usually the roofs of caves, even in the large hollow hills, isn't enough to kill or even seriously injure most mobs. Also, sending them outside means they can't somehow hurt you as they fall (skeletons in particular are frighteningly good at midair revenge shots).
