Gary Gygax’s 1979 module B2: The Keep on the Borderlands is the foundational text of the sandbox campaign. Ostensibly written as an introductory adventure for the D&D Basic Set, it functions under the hood as a masterclass in dynamic world-building, spatial economics, and emergent play. This is going to pick right up from OSR Commentary - Adapting AX2: Secrets of the Nethercity For ACKS II rpg & Barrows & Borderlands Rpg
When peeled back from its nostalgic veneer, B2 reveals a sophisticated, highly volatile ecosystem built on factional tension, economic vulnerability, and a stark, unromantic view of the frontier.
1. The Geometry of Isolation: The Keep's Spatial Design
The Keep itself is not just a safe zone; it is a pressurized container of Law perched precariously on the lip of Chaos. Its architectural layout dictates the social dynamics of the campaign.
The Outer Bailey (The Buffer Zone): This is where commerce, transience, and vulnerability live. The tavern, the inn, and the stables form a economic engine designed to extract coin from travelers and mercenaries. It is deliberately exposed; if the outer wall falls, the outer bailey is sacrificed.
The Inner Bailey (The High-Trust Engine): Separated by a secondary massive gatehouse, the inner bailey houses the Keep’s actual power structure—the Castellan, the guard garrison, and the chapel. This physical segregation tells low-level PCs exactly where they stand: they are tools of the state, kept in the courtyard until they prove their utility.
The Structural Flaw: The Keep is a logistical nightmare if cut off. It relies entirely on a single, vulnerable trade road to the civilized lowlands. A clever Game Master realizes that the human factions here are just as desperate for stability as the monsters in the caves are for territory.
2. The Caves of Chaos as a Fractured Megadungeon
The Caves of Chaos are frequently misread as a "monster zoo"—a random assortment of humanoids crammed into a single ravine. In practice, they represent a highly sophisticated, multi-tiered tribal ecosystem.
The ravine acts as a literal corporate ladder of absolute savagery, arranged vertically and deeply divided by evolutionary and cultural hatreds.
[ The Dark Chapel ] (The True Threat)
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[ Minotaur ] <---> [ Gnolls ]
^ ^
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[ Orcs: Tribe A ] <=======> [ Orcs: Tribe B ]
^ ^
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[ Goblins ] <-------------------> [ Hobgoblins ]
^
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[ Kobolds ] (The Bottom Feeders)
The Geopolitical Fault Lines
The Grudge Match: The two rival Orc tribes (Tribe A and Tribe B) hate each other with a fury that rivals their hatred for the humans. If PCs clear one side, they actively grant a regional monopoly to the other.
The Underclass Wars: The Kobolds at the bottom of the ravine are food and slave labor for the Goblins and Hobgoblins. They are structurally incapable of winning a prolonged war, making them prime candidates for PC exploitation, bribery, or asymmetrical warfare.
The Hidden Hegemony: At the apex sits the Shrine of Evil Chaos. The cultists are not merely cave dwellers; they are the ideological puppet masters using religious terror and wealth distribution to prevent the humanoids from tearing each other apart before they can overwhelm the Keep.
3. The Undercurrent of Borderland Economics
Gold and silver drive B2 more than any grand narrative of good versus evil. The module operates on a strict zero-sum economy that forces players into grey moral choices.
| Faction | Primary Economic Engine | Vulnerability |
| The Keep | Trade taxes, mercenary exploitation, state supply lines | Total reliance on external grain/goods shipments |
| The Humanoids | Raiding trade caravans, internecine tribute | Absolute lack of agriculture or sustainable production |
| The Cultists | Plunder, ideological funding from external dark powers | Exposed supply lines if the ravine is blockaded |
The Realities of Gygaxian GP
Because early editions tie character advancement (XP) directly to recovered treasure, the game mechanics force PCs to act as state-sanctioned looters. Every gold piece stripped from a goblin chief’s chest is capital removed from the local wilderness economy and injected into the Keep’s merchant lane.
This creates an inevitable cycle: looting causes tribal desperation, desperation causes increased raids on the trade roads, and increased raids force the Castellan to fund more desperate expeditions into the ravine.
4. The Hidden Catalyst: The Wilderness
The wilderness hexes between the Keep and the Caves are not empty transit space; they are a ticking clock.
The Mad Hermit: A textbook example of borderland madness. He represents the fate of those who reject both the rigid martial law of the Keep and the tribal collectivism of the Caves.
The Lizardmen: Positioned in the southern fens, they are a neutral wildcard. They do not care about the geopolitical war between the Castellan and the Cultists, but their territorial integrity controls access to the riverways.
5. Turning the Key: Running B2 with Modern Intent
To elevate B2 from a classic crawl into a dynamic, shifting campaign, a Game Master needs to treat the module as a loaded spring. The moment the PCs arrive, the balance of power should begin to crack.
Weaponize the Factions: Let the humanoids negotiate. A dying goblin chief should gladly offer the PCs a map of the Hobgoblin complex in exchange for his tribe’s survival.
Track the Logistical Fallout: If the players kill the Kobolds, who moves into their caves? The Orcs? Or does the gelatinous cube wander out of the depths because its food supply has dried up?
The Keep is Not Safe: The cult has agents inside the walls. The lonely, isolated mercenaries in the Outer Bailey are prime targets for subversion, bribery, and religious radicalization.
To bridge the foundational sandbox of B2: The Keep on the Borderlands with the granular, socio-economic engine of Adventurer Conqueror King System II (ACKS II) is to transform a classic introductory dungeon crawl into a highly volatile, politically charged borderland simulation.
Where early editions of D&D treat the wealth and manpower of the Keep as static background flavor, ACKS II mechanics demand that every coin looted, every mercenary hired, and every goblin tribe displaced ripples directly through the local market economy and domain stability.
1. The Keep as a Class VI Market (The Borderland Frontier)
In ACKS II, settlements are categorized by Market Classes, which dictate the availability of goods, the maximum value of items that can be sold, and the weekly pool of mercenary talent.
The Keep functions as a Class VI Market (a tiny frontier settlement or fortified outpost).
[ Civilized Lowlands ] ===(Trade Income: High)===> [ The Keep: Class VI Market ] ===(Target)===> [ The Caves of Chaos ]
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[ Frontier Garrison ]
(High Upkeep / Low Tax Base)
The Economic Squeeze
The Monthly Supply Limit: A Class VI market has a limited monthly supply of standard equipment and a very low threshold for purchasing monster treasure. If the PCs return from the Caves of Chaos with a hoard worth $3,000\text{ gp}$, they cannot simply liquidate it at the local provisioner. The local merchants lack the liquidity. The PCs must either pay a hefty premium to ship the loot to a larger city downriver, barter directly with the Castellan for land/favors, or accidentally crash the local frontier economy by causing hyperinflation.
Mercenary Scarcity: The Outer Bailey tavern is not an infinite well of meat-shields. In ACKS II, a Class VI market might only generate $1\text{d}4$ Light Infantry or Bowmen candidates per month. If the players treat their retainers as disposable trap-detectors in the ravine, they will rapidly find themselves entirely alone; word spreads that expeditions with the PCs are a death sentence, drying up the local labor pool.
2. The Caves of Chaos as a Fragmented Beastman Domain
Instead of seeing the Caves as a random assortment of monster lairs, ACKS II views the ravine through the lens of Beastman Tribes and Domains. The Caves represent an active, competitive ecosystem of overlapping tribal territories fighting for the same limited resources.
Using the ACKS II domain management logic, the Ravine can be mapped out as an unstable web of tribal dynamics:
| Tribe | ACKS II Unit Types | Primary Resource | Territorial Strategy |
| Kobolds | Light Infantry (Slingers), Skirmishers | Numbers & Hidden Tunnels | Subservient to the Hobgoblins; focus on ambush and defense. |
| Goblins | Wolf Riders, Light Infantry | Mobility & Warg Breeding | Attempting to secure the Wilderness Road to intercept commerce. |
| Orcs (Tribe A/B) | Heavy Infantry, Medium Infantry | Martial Might & Raiding | Locked in a blood feud over hunting grounds and tribute. |
| Hobgoblins | Phalanx Infantry, Heavy Infantry | Discipline & Tactical Fortifications | Functions as the military backbone of the ravine, policing lower tribes. |
| The Cult | Cultists, Dark Pluralists, Anti-Clerics | Divine Favor & Unholy Relics | The shadow government extracting tribute to fund a chaotic node. |
The Chieftain's Balance Sheet
In ACKS II, monster chieftains must pay their troops and feed their populations just like human rulers. The humanoids in the Caves are starving; the frontier is over-populated.
If the PCs cut off the Goblins’ access to the trade road, the Goblin Chief faces a resource crisis. To prevent a mutiny, he must either launch a desperate, suicidal assault on the Keep’s supply lines or invade the neighboring Orc territory to seize their grain stores.
The players can actively use Subversion and Bribery (ACKS II Criminal Syndicate rules) to fund one faction, turning a dungeon crawl into a proxy war.
3. The Castellan’s Dilemma: Garrison Costs vs. Revenue
The Castellan is not just an NPC who gives out quests; he is a Domain Ruler operating on a razor-thin financial margin.
The Keep maintains a formidable garrison: dozens of heavy footmen, crossbowmen, and cavalry. In ACKS II, the monthly upkeep for a professional military force of this size vastly outstrips the tax revenue generated by the tiny civilian population in the Outer Bailey.
+-------------------------------------------------------+
| THE CASTELLAN'S MONTHLY LEDGER |
+-------------------------------------------------------+
| REVENUE: |
| - Outer Bailey Market Taxes: +150 gp |
| - Royal Borderland Subsidy: +1,200 gp |
+-------------------------------------------------------+
| EXPENSES: |
| - Garrison Wages & Rations: -1,800 gp |
| - Wall Fortification Maintenance: -250 gp |
+-------------------------------------------------------+
| NET MONTHLY DEFICIT: -700 gp |
+-------------------------------------------------------+
The Strategic Consequence
The Castellan is hemorrhaging money. The royal court in the civilized interior will only subsidize this outpost for so long before deciding the borderland is a lost cause.
The PC as an Investment: This financial pressure is exactly why the Castellan tolerates rowdy, heavily armed adventurers operating out of his tavern. He needs the PCs to clear the caves because his official garrison cannot leave the walls without risking the Keep falling to an immediate siege.
The Taxman Cometh: Once the PCs start clearing sections of the Caves, the Castellan will assert legal claim over the recovered territory under crown law. He will demand a tithing or treasure tax (typically 10% to 20%) on all bullion brought through the Keep's gates to balance his ledger, creating a natural point of friction between the party and the law.
4. The Campaign Endgame: Securing the Borderlands
The ultimate synergy between B2 and ACKS II emerges when the party survives to mid-levels ($4\text{th}–6\text{th}$ level) and shifts from mere delvers to domain rulers. The module naturally transitions from a dungeon crawl into a Borderland Clearing Simulation.
[ Level 1-3: Tactical Crawl ] ---> [ Level 4-5: Factional Sabotage ] ---> [ Level 6+: Domain Construction ]
- Loot for XP - Fund Tribal Wars - Clear Hexes
- Hire Local Retainers - Intercept Cultist Supply Lines - Build Borderland Strongholds
From Ravine to Barony
Under ACKS II rules, to claim a domain, the wilderness hexes must be systematically "cleared" of monsters.
The Purge: The Caves of Chaos cannot simply be left half-empty. If the Cult is destroyed but the Hobgoblins remain, the domain is still considered wild. The players must systematically root out or subjugate every faction.
Vassalizing the Humanoids: An enterprising Lawful or Neutral PC might choose not to exterminate the remaining humanoids, but to force them into vassalage. Using the ACKS II Monstrous Vassals mechanics, a defeated Orc chieftain can swear an oath to a player character, turning the remaining cave complexes into a fortified, subterranean march that guards the PC’s new border territory.
The Shadow War: If the players build a stronghold nearby, they must contend with the Unholy Node generated by the Shrine of Evil Chaos. Until the shrine is desecrated and ritually purified by a high-level cleric, it will continuously attract new chaotic monsters to the region, increasing the local Savage Encounter rate and suppressing civilian migration to the players' new lands.
5. Master Faction Conflict Table for the Borderlands
This d20 table represents the regional friction between the Keep's supply lines, the competitive humanoid tribes, and the machinations of the Cult, processed through ACKS II wilderness movement mechanics.
| d20 | Encounter Type | Factions Involved | Economic / Tactical Consequence |
| 1-2 | Tribal Skirmish | Orcs (Tribe A) vs. Goblins | The Orcs are executing a punitive raid on a goblin foraging party. Left alone, one side is wiped out, shifting the balance of power in the ravine. |
| 3-4 | Cultist Supply Interdiction | The Cult vs. Keep Caravan | Hooded acolytes and undead skeletons are ambushing an iron shipment meant for the Keep's blacksmith. Success increases the cost of weapons at the Keep by 20%. |
| 5-6 | The Desperate Levy | Keep Garrison vs. Wilderness | A squad of Keep footmen is forcibly press-ganging local laborers and travelers into service to replace recent casualties. PCs must negotiate or see their preferred torchbearers drafted. |
| 7-8 | Tribute Collection | Hobgoblins vs. Kobolds | A disciplined phalanx of Hobgoblins is extracting food and copper from a terrified pack of Kobolds. If the PCs protect the Kobolds, they earn a fragile, low-trust informant network within the Caves. |
| 9-10 | The Mad Hermit’s Market Disruptor | The Hermit vs. Local Ecosystem | The Mad Hermit has trapped a live monster (e.g., a Owlbear or Gray Ooze) and is attempting to steer it toward the Keep’s trade road to drive away "the civilized insects." |
| 11-12 | Mercenary Desertion | Disgruntled Guards vs. The Law | $1\text{d}6$ heavy infantrymen have deserted the Keep due to back-pay issues and are turning to highway robbery. They possess inside knowledge of the Keep’s watch schedules. |
| 13-14 | The Fens Encroachment | Lizardmen vs. Orcs (Tribe B) | Lizardmen from the southern swamp have traveled upriver to contest a watering hole used by the Orcs. The area is a chaotic three-way hunting ground. |
| 15-16 | Underground Railroad | Cultist Infiltrators vs. The Keep | A seemingly mundane merchant wagon leaving the Keep is caught smuggling sacrificial victims or silver out to the Shrine under the cover of night. |
| 17-18 | The Warg Run | Goblin Cavalry vs. Trade Caravan | Goblin wolf riders are performing a hit-and-run raid on a luxury trade caravan. Wealthy merchants from the lowlands are trapped; saving them offers a direct line to Class I market financing. |
| 19-20 | Total Ravine Mobilization | The Cult’s Vanguard | A unified force of Orcs, Goblins, and Cultists are marching to establish a forward siege camp outside the Keep's valley. The campaign sandbox has escalated to an open war footing. |
