The last game I DM'ed this past December used B2 The Keep On The Borderlands as the main setting. The common criticism of this module is the fact that all of these different humanoid tribes live in close proximity with each other with relatively little conflict or cooperation one way or the other. In my efforts to expand the module contents, I'm going to propose a reactionary system for the inhabitants of the Caves.
[Note: Not like I'm actively DMing at this point, but if the ideas start floating around in my head, I might as well put them down.]
In order to impose some kind of system for the humanoids to react to incursions by adventurers, I need to create a framework for an ad hoc organization of the tribes as a whole. Ostensibly, the evil cleric in the temple cave is a cleric of the Elder Elemental God, also providing a hook into the Temple of Elemental Evil as an expansion to the B2 campaign area. If the PCs discover the link, or bring back evidence to the Curate in the Keep, it will provide a hook for a trip to Hommlett.
Even though this Cleric would be chaotic in nature, he still exerts a degree of control due to his power and small legion of zombies and acolytes. If the PCs are on the verge of breaking the Caves and scattering the tribes within, the Cleric will lose his influence and be forced to hole up in his Temple or hatch some other evil plan. This will form a basis for loosely uniting the tribes in reaction to PC incursions. Overall, the individual reactions of the tribes will be on a local level, basically, an increased state of alertness and defensive postures within their caves. On the larger level, as the PCs begin to put a dent into the Caves, a more concerted effort will be put forth by the baddies to prepare for adventurers.
This provides a loose context for establishing a relathionship between tribes of humanoids that would otherwise be warring each other. Some of the Caves that house baddies like the Ogre and Minotaur still work. The Ogre can still be a "mercenary" of sorts to the Goblins; as long as the Ogre is doing more damage outside the Caves than inside, the cleric would not interfere. The Minotaur continues to subside on sacrifices and enjoys ruling his little maze-like domain. Both of these heavy hitters provide an opportunity for the Cleric to use them in interesting situations if need be, such as an expensive bodyguard or even a magically controlled pawn.
The system here will be a simple counter that accumulates every time the PCs raid the Caves with a weight based on the amount of damage they do. I'll put forth a working list of what actions will increment this Threat Level and what value will warrant a response and the form of that response.
[I started to specify actions with a particular point value, but scrapped that in favor of a qualitative system, leaving it more open to interpretation and improvisation rather than a rigid system.]
Nuisance increments to Threat Level:
* Spotting adventuring parties within the ravine or actually encountering the inhabitants of a cave.
* Raiding the Kobold cave, even if the entire tribe is shattered. These guys would be the lowest on the totem pole, only allowed to exist in the complex due to the fact that they are decent cannon fodder. Also allows the PCs to at least have access to some combat experience without having all the Caves on high alert.
* Killing a small number of humanoids, such as during a wilderness random encounter or a limited skirmish inside the caves.
* Killing a significant number of Goblins in Cave D, but not shattering the tribe.
Ultimately, these actions can be taken without any real organized reaction.
* A serious raid into the lower level caves (Goblins in D) that results in shattering the tribe, killing the chief, or otherwise putting the Goblins out of action. While still low on the totem pole, Goblins are at least enough of a challenge to alert the rest of the tribes that there is a competent force of adventurers lurking.
* Killing the Ogre (Cave E). The Ogre represents a significant foe and would rouse the other tribes.
* Similarly, the Owl Bear in Cave G.
* A raid into the middle level caves (the Orcs in B and C, Hobgoblins in H, Bugbears in F) that defeats a significant number of monsters, roughly a large encounter's worth, but otherwise leaves the tribe intact. These troops represent a significant force for Chaos, so casualties will be felt.
* Killing the Minotaur in Cave I. Only seasoned adventurers and do-gooders would be capable of navigating the maze and slaying the Minotaur.
* Causing massive casualties to one of the middle level caves, including killing the chief or shattering the tribe. This would be a severe blow to Chaos' manpower.
* Raiding the Temple Cave K. Even a minor encounter and a few slain zombies would be taken personally by the Cleric.
* Any significant raid into the Temple cave would probably be the highest insult short of actually killing the Cleric himself.
A single minor threat would force a guard to be placed at the entrance to the ravine. This would be a large group of kobolds (if left alive) as a disposable warning force, or a group of goblins that would be capable of putting up a fight before falling back. Multiple minor threats would increase the guard's presence at the ravine mouth, up to a 24/7 watch and a few mobile groups of Orc, Hobgoblins, or Bugbears patrolling about a quarter mile around the Caves. This is probably the maximum amount of organization that could be enacted given the mash-up of species. Patrolling groups would fight any adventurers found; a severely outmatched patrol would either flee to reform later or possibly fall back to combine with other patrols/guards. Patrols are also a great opportunity to ambush adventurers after they have finished a raid and are burdened with loot.
A single major threat by itself would prompt a full guard compliment at the ravine and around the caves. A major threat plus some lingering minor threats would provoke a counter-attack as detailed below. Multiple major threats or a raid into the Temple would provoke the harshest counter attacks from below, assuming the Caves still had significant manpower available.
* The Cleric would lead a contingent of forces to attack the ramshackle town outside the Keep along the river. (I added this to expand the Keep setting; populated mainly by refugees from the Giant incursions happening in Geof). The primary goal of the raid would be a quick attack to gain prisoners and corpses to animate as zombies.The incursion would seek to avoid confrontation with the Keep's forces. The PCs could get involved with a running battle to attempt to save the would-be slaves or even a quick follow up rescue mission. Or just not care.
* If a particular band of adventurers has really caught the ire of the Cleric, such as raiding his Temple, the Cleric would arrange to have the PCs killed. This could lead to a number of different encounters. The brigands or wild men could be hired out to stalk and attack the PCs after they leave the Keep. The Hermit could be charmed into entering the Keep and attacking the PCs, kind of a medieval suicide attack. If the adventurers use the same path to access the Caves multiple times, the tracks could be found and a nice deadly trap laid. The acolytes of the Cleric could try to gain entry to the Keep, sign on with the PCs as henchmen/hirelings, and lead them to their doom in the Minotaur Cave or an ambush in the Temple. Any or all of these tactics could be used to fight back against a group that has the Caves on the ropes.
Overall, this puts a couple good ideas down in writing to further expand B2, help develop the low-level campaign setting, and help add some dimensions to the classic dungeon romp module. The end goal would be to add enough content to the area to have the PCs run up to at least 3rd level up to 5th level with enough planned content and opportunities for improvised situations without necessitating a railroad to completely clear the Caves. Getting a single group of adventurers to this level would really be a solid start to a lasting campaign.
Some other ideas floating around in my head including B1 in to the relative area. Possibly farther up in the mountains off to the NW of the mapped area. A few hooks could be sprinkled in to integrate the new adventure location. But that would be a separate post.
So I hope you enjoyed my entirely too long, rambling posts... At least they serve to get my thoughts down for the day I actually resume DMing...