To begin, we have to establish two sets of facts about the Caves:
1. Who or what built, used, and inhabited it in the past, and
2. Who or what inhabits it now.
To preserve the central premise of the Caves, I'll continue to assign each area to different, mostly-mutually-hostile factions. This both produces variety, and explains why there isn't an effective defense against PC incursions into the Caves.
Some of the history should tie into why the current inhabitants are there, but some should be new arrivals as well, and each faction requires some sort of goal that they purse in the Caves.
History of the Caves
For this exercise, let us assume a world that is broadly the same as the Red Box presents it — there is a human civilisation, somewhere, but it is not here. Elves, dwarves, et cetera live in small clans and feud amongst and between themselves. Orcs and goblins are less friendly than the elves and dwarves, but possess their own societies as well. This should inform the situation locally, in the Caves.
To start with, let's say the Caves were built by elves, the oldest civilisation. Their original purpose were as tombs, rock-cut tombs set into an old gully. Because the exterior of the Caves are somewhat nondescript and a little boring, let's add some sort of fantastic detail to liven it up and try to communicate the idea that it was created by elves: the stump of a giant, petrified tree at the top of the gully (roughly above area XX). Petrified roots stretch across the sides of the gully, and the doors to each area are built into the negative spaces. The doors of each area are carven trilithons. This might mean that the first chambers of each area are the oldest, although the shape of most of the Caves (especially the north and south areas) implies whole sections were constructed at once. Conversely, Areas I and X might never have been deliberately excavated at all.
The monumental nature of the tombs implies that they were made for important people, and perhaps to commemorate those who died in some monumental battle or from some notable dynasty. We can put aside the specifics thereof until later, but we should keep that in mind while stocking decorative elements and specials.
To fill in the history of the Caves, post-construction, we'll layer on strata of occupiers, each having put their own mark on the complex. I'll leave aside describing the process of brainstorming these specifics, but in general I want a history of conflict and different reasons for occupation, in order to create the groundwork for justifying different factional interests in the Caves:
The Caves were first excavated by elves as a tomb complex. Later, they were occupied by a cadre of dwarves, who defiled and expanded them during their ancient wars with the elves and goblins. The dwarves, too, were killed and driven out by orcs and goblins, who then occupied the caves before being driven out by other clans. The Caves exchanged hands many times in the long, dark ages since then. The death-energies of the place attracted undead, diabolists and necromancers, but their hold on the Caves have been broken by the recent return of a secretive elven cabal.
Next time, we'll figure out the large-scale question of who's in what area of the Caves, and how those areas interrelate with each other.
