"They've all got a core, it's a thingy about the size of a basketball, and if you destroy the core the rest of the dungeon collapses in a few minutes, killing anyone inside. If you don't do that, then eventually after like a couple weeks of kidnapping people and producing monsters and stuff, the dungeon will go away on its own, again killing anyone inside, and then it'll come back bigger and meaner in months or years. The first upgrade is usually the most substantial but it continues indefinitely; the worst dungeons are all ones that got away in the early days and have kept doing so since then. If the dungeon dies while its monsters are outside of it, sometimes they vanish or disintegrate or something, but sometimes they stick around, there's a few of those around. Some of them talk. Usually the monsters of an active dungeon do not talk. Some dungeons are four dimensional inside. Dungeons can contain substances that we have not invented or that retain magical properties after removal from the dungeon, too, some of which can even be reverse engineered, and those are big in the materials science sector."