So I was wandering along in Hell today building myself a nice bridge ready to kill the WOF, when suddenly above me I noticed some nice blue bricks. Upon closer inspection I realised that it was actually the very lowest point of the dungeon. I tunnelled through and so now have a (handy?) back door into the dungeon but it got me wondering:
If I hadn't already killed Skeletron, what would have happened? I assume I'd be killed at some by the guardian things, but where? I had to tunnel through a fairly thick wall so at some point half way through the wall would I suddenly become "in the dungeon"?
Best Answer
According to the official Terraria wiki, you should avoid getting too close to the dungeon from underground, if you haven't defeated Skeletron yet.
This means that you do not need to actually be inside the dungeon for the Dungeon Guardian to spawn. The reason for this, is because the Dungeon is not a closed space; in my world for instance, the dungeon was generated with a patch of dirt separating two patches of wall, so I could've entered the dungeon without actually digging through its wall.