Thanks all! Glad I wasn't the only one scratching my head!

I checked in with the Discord helpers, apparently there was a bug so you could accidentally see the black boxes around dungeons from the ground. That should be fixed now.

I assumed it's related to object-culling, done as a performance optimisation. I don't know what was broken... whether it wasn't culling enough (wasting GPU) or was too aggressive (some people seeing glitches). Whatever the case, I'm assuming most people didn't and won't notice a difference, hence the obscure note.

I wanna know too lol i read it like 10 times trying to figure it out haha

Maybe problems with the secret doors in the mistland dungeons. Or a fix fix to what I had; A window in a dungeon you could look at a core but not pick it up.

I dunno either, but I just started a new game. My first three burial chambers yielded 5 cores, 3, 1 and 1. Could just be bad RNG

Talking about a Black Mistland core ;-)