Running Gary Gygax’s classic megadungeon modules D1-2: Descent into the Depths of the Earth using Adventurer Conqueror King System II (ACKS II) transforms a straightforward dungeon crawl into a campaign of logistics, domain warfare, subterranean colonization, and trade empire building. This blog post picks right up from OSR Module Campaign Commentary - Combining S4 The Lost Caverns of Tsojcanth and W4 The Forgotten Temple of Tharizdun With ACKS II rpg
While AD&D 1E treats the passage through the Underdark as a continuous linear skirmish against drow patrols, ACKS II mechanics fundamentally alter how this adventure plays out. The system provides strict rules for Supply & Load (Supply Track), Domain & Market Operations, Cleave Mechanics, and Warfare (via Domains & Monster Throngs).
Here is a breakdown of how to run and expand D1-2 for ACKS II.
1. System Mechanics & Mechanical Conversions
ACKS II relies on precise mathematical conversion from AD&D 1E:
Armor Class & Throws
Armor Class: Convert 1E AC to ACKS II using
$\text{ACKS AC} = 9 - \text{1E AC}$. Example: A Drow in chainmail + shield with AC 2 becomes ACKS AC 7.
Attack Throws: Drow and elite subterranean combatants use standard ACKS II combat progressions (Fighters/Crusaders).
Drow hit die numbers stay the same, but gain Cleaves equal to their level or HD. Saving Throws: Map AD&D saves directly to the 5 ACKS II categories: Blast/Breath, Lethal, Poison, Spells, or Devices.
Drow Poison & Magic Items
Drow Sleep Poison: Resolves as a Save vs. Poison. A failed save causes unconsciousness for $2\text{d}4$ hours.
Underdark Metal Decay: Drow $+1$ to $+3$ adamantite weapons and armor decay when exposed to direct sunlight (losing $+1$ bonus per day until becoming mundane iron). In ACKS II, these count as Artisan Quality or Minor Magic Items while underground, giving high trade value within the Underdark market economy.
2. Supply, Exploration & Logistics
In D1-2, the party travels through miles of lightless, damp primary and secondary passages. In standard 1E, encumbrance is often hand-waved; in ACKS II, supply management makes subterranean travel a survival puzzle.
┌────────────────────────────────────────────────────────────────────────┐
│ PRIMARY UNDERDARK PASSAGES │
│ │
│ [ Surface Outpost ] ──(1 Hex / 6 Miles)──► [ Drow Checkpoint Hex D3 ] │
│ │ │
│ (Mercantile Trail) │
│ ▼ │
│ [ Vault of the Drow ] ◄──(Kuo-Toa Waters)── [ Shrine of the Kuo-Toa ] │
└────────────────────────────────────────────────────────────────────────┘
Supply Rations & Water:
Fresh water is rare; much of the underground water is contaminated or brackish. Characters require standard ACKS II water/rations.
Carrying capacity mandates using pack lizards, porters, or subterranean beasts of burden.
Marching & Navigation (Dungeon & Wilderness Merged):
High-tier passages count as Difficult Underground Terrain.
Exploration shifts between Turn-based Delving (inside cavern encounters like Hex D3 or the Kuo-Toa Shrine) and Hex Crawling (6-mile hexes through primary tunnels).
Navigating Throws: A party without a subterranean guide or specialized proficiency (Underdark Navigation, Spelunking) must make daily Navigation Throws to avoid getting lost in looping secondary tunnels.
3. The Underdark Economy & Mercantile Operations
ACKS II features robust market and trade rules. In D1-2, Drow merchant trains and slave convoys move between the surface and the Vault of the Drow.
Underdark Market Modifiers
Treat the Kuo-Toa Shrine (D2) and Drow Outposts as small-to-medium markets:
| Commodity | Demand Modifier | Rationale |
| Grain / Foodstuffs | $+3$ (High Demand) | No arable land; surface crops are luxury goods. |
| Common Wood / Lumber | $+3$ (High Demand) | Used for shaft supports, scaffolding, and shields. |
| Fungi, Spores & Lichen | $-2$ (Low Demand) | Abundant local production. |
| Slaves / Servants | $-1$ (Moderate Supply) | Active slave trade by Drow and Kuo-Toa. |
| Rare Metals / Adamantite | $-2$ (Low Demand) | Locally mined and forged. |
Merchant Convoys & Caravans
When the party encounters a Drow Merchant Train, treat it as an active trade node:
Loot & Cargo: Convoys carry trade goods (surface surface lumber, silk, wine, or subterranean gems/ores).
Tactical Value: Capturing a Drow trade train grants high-value ACKS II trade units, but instantly alerts neighboring Drow garrisons, raising the Local Suspicion / Alert Level.
4. Expanding D1-2 into ACKS II Domain Play
The original module is designed for High-Level PC infiltrators. In ACKS II, level 9–14 PCs are Conquerors and Kings. They shouldn't just be 4–6 adventurers sneaking down a corridor—they will likely bring an army, establish strongholds, and claim territory.
┌───────────────────────────────┐
│ Surface Realm / Domain │
└───────────────┬───────────────┘
│ (Forward Supply Lines)
▼
┌───────────────────────────────┐
│ Underdark Garrison / Fort │
│ (Hex D3 Checkpoint Base) │
└───────────────┬───────────────┘
│
┌───────────────────────┴───────────────────────┐
▼ ▼
┌───────────────────────────┐ ┌───────────────────────────┐
│ Domain Action: Colonize │ │ Domain Action: War │
│ Fortify secondary tunnels │ │ Siege on Shrine of │
│ & extract mineral veins │ │ Kuo-Toa (Module D2) │
└───────────────────────────┘ └───────────────────────────┘
Expanding Encounter Areas into Strongholds
Hex D3 Checkpoint: In the module, this is a Drow guard station. In ACKS II, turning Hex D3 into a Subterranean Forward Operating Base (FOB) allows PCs to secure a domain footprint underground.
Cost to fortify: Standard ACKS II construction costs ($10,000–$50,000\text{ gp}$ to stone-seal tunnels, install portcullises, and set ballistas).
Garrisoning: Requires mercenary light infantry, crossbowmen, and dwarven sappers.
The Kuo-Toa Shrine (D2): The shrine complex functions as an Underdark Urban Domain / Vassal State.
The Kuo-Toa hate the Drow but trade with them out of necessity. High-level PCs can use Diplomacy / Domain Intrigue to incite a Kuo-Toa rebellion against the Drow, turning the shrine into an allied trading domain rather than simply massacring the inhabitants.
Mass Combat & Domain Warfare
When Drow counter-attack forces or Kuo-Toa war bands mobilize, resolve the battle using ACKS II Campaign Warfare Rules:
Drow Platoons: High-morale, high-initiative light infantry equipped with hand-crossbows (ranged volley capabilities) and sleep-poisoned bolts.
Bugbear Shock Troops: Heavy infantry auxiliaries used by Drow commanders to breach PC phalanxes.
Kuo-Toa Levies: Mixed polearm/spear infantry backed by high priests (Crusader/Cleric equivalent) utilizing area-of-effect defensive magic.
5. Campaign Progression (The GDQ Arc in ACKS II)
Using ACKS II rules turns the G-D-Q mega-campaign into a grand strategic campaign:
G1-3 (Giants): The PCs defeat the giant leaders on the surface and uncover the Drow conspiracy.
D1-2 (Descent): PCs establish an underground campaign theatre. They clear tunnels, secure supply lines, build fortified subterranean outposts, negotiate trade treaties with Svirfneblin or Kuo-Toa, and choke off Drow supply routes to the surface.
D3 (Vault of the Drow): PCs march armies or elite strike-teams into the Vault, engaging in noble house politics, factional domain warfare, and economic sabotage.
Q1 (Queen of the Demonweb Pits): The planar finale, where realm-level magic and divine ascension mechanics take center stage.
Summary Advice for the Judge
Track Encumbrance & Light: Enforce torch/lantern consumption and supply slots. Darkness in the Underdark is a lethal tactical hazard.
Embrace Cleaves: PC Martial classes (Fighters, Dwarven Vaultguards) will chew through minor Drow/Bugbear skirmishers quickly due to ACKS II Cleave rules. Counter this by utilizing Drow ranged ambushes, darkness spells, choke points, and tactical retreats.
Reward Domain Thinking: If the players want to mine the rich iron and gem veins mentioned in the module text, let them bring down miners, set up domain infrastructure, and defend their claims against Underdark raiders.
