Typically, your character will exclaim they're in the wrong crypt when they reach the end portal stone in the Cemetery. In one of the dungeon blocks of incorrect crypts, there is no such end portal, but your character will remark that you've found a dud. I believe this voice over should only be played when finding that blue stone. Sorry, no screenshots available.
Hey Tobias, your character says that the cavern "is a dud" to let you know that the crown is not in that dungeon. He says it early so you can turn around and leave if you want, or keep exploring to finish the dungeon.
