Originally posted by umop-apisdn:

There's a blob in one of my swamp crypts that I can't find... but I can hear it splorching and splashing around. This isn't restricted to Infested Mines.

Originally posted by ritt5220:

Some times I have enemies spawn inside big rocks in the black forest. You can here them and if they have a bow or rock they can hit you. I guess the same is true about mines and crypts, they spawn inside a wall, but you can not break the walls so you will never find them.

Originally posted by umop-apisdn:

It should be noted that placing a portal "backwards" can put you inside a large boulder, too... and you can see out of it (on any faces that are uncovered on the outside) and shoot through it, too... although apparently unlike mobs, exiting is as simple as walking out of it.

Those big rocks in the plains are more useful than you may have thought.

https://youtu.be/ky9xo_UwQAA?t=426
(The plains boulder how-to starts at ~ 7:06)

Originally posted by Ciuy:

i had undead and other fauna spawn from close proximity nests inside the mud piles, like archers. Had to pickaxe it to reach him. Sometimes i get blobs stuck on Top of the mud pile outside or inside the wall, top of the tunnel the pile is blocking; unreachable. Yes it`s a spawning issue. No collision detection, just spawn.

Originally posted by ling.speed:

Its possible but personally i never encountered such situation, its always some special passage. (playing unmodded, mods could make this more of a problem). There is quite a bit of variation in any caves. You may go through 20+ caves of the same type and see a new type of passage still on the next one.