Basics, Part 5

Occupancy 

The dungeon occupancy rate is less than 20%, with the majority of rooms empty of inhabitants. An adventuring band will not find an orc with a pie in one room and an ancient red dragon across the corridor.

The occupants of rooms frequently follow tribal or creature lines, and a groups of rooms are often inhabited by tribes of similar humanoids (though that does not preclude mixed tribes of creatures) with empty rooms serving as a buffer-zone or no-man's-land between rival groups.

Dangerous monsters will be given a wide berth by other denizens, so the buffers of empty rooms around their territories will be larger, dependent on the size of the beast.

Changes

The Ring Vaults changes itself around as time goes on. Sure, some of the creatures that inhabit it add a corridor here or there or divide off a room or two, but the majority of changes occurs within the dungeon itself.

Some of it is subtle, a door changes in some way, moves down the corridor a little or disappears entirely. Some of it is less so, with whole areas of the vaults disconnected from others for unknown reasons and lengths of time.

Often these changes are linked to the phase of the moon or the sun or the stars (or even other, more mysterious conditions), while some are linked to situations (there is a room in the Ring Vaults that hides from elves - no elf or party that includes an elf can ever find it).