I just got MultiVerse and created a new survival world.
I was surprised that I spawned in a dungeon. Is this a 'nothing special' type of thing or is it very rare?
If so, what might be the odds of spawning in a dungeon?
Given the vast amount of seeds available and the size of the world, happening to spawn in a small dungeon of all places in a nearly infinite world is very unlikely to happen. Even exploring they can hard to find. Because of the amount of possible combinations of seeds it's impossible to define a precise chance of this happening.
Short Answer: Less than 1/100 chance you'll spawn in a spot from which you can hear a dungeon. Less than Approximately 1/8000 chance that you'll spawn in a dungeon.
Long Answer: I am in the process of clearing out a 200 x 200 area for a witch farm. In that clearing out process I have found 5 dungeons between approximately Y values of 40 and 64 (I haven't gotten down to the lower parts yet in my clearing). 1 of which is just at the surface. We'll assume I've found them all and that these are typical numbers.
Each dungeon can be heard from the top in (best case, so this is over estimating things) a radius 16 circle, so that's roughly 800 squares from which you can hear one of these dungeons. They are so far apart, so we get 4000 squares that you can hear a dungeon from in this region. Or, 1/100 chance that you can hear a dungeon from your spawn point.
Assuming all these dungeons are on the surface (which ain't true) each takes no more than 49 squares. So that's 5*49 ~ 250 squares total. So, 250 / 40,000 = 160.
In actuality, in my 200x200 region, there is one dungeon basically on the surface, assuming that's typical, then it ends up being more like, 50 / 40,000 = 1/8000