Combining S4 The Lost Caverns of Tsojcanth and W4 The Forgotten Temple of Tharizdun is one of the most natural and rewarding classic D&D module combinations available. Written by Gary Gygax in 1982, W4 was specifically created as an direct sequel to S4. Both modules share the Yatil Mountains setting, an intertwined lore involving the Dark God Tharizdun and the archmage Iggwilv (Tasha), and complementary dungeon styles.
1. Lore & Narrative Integration
The two modules fit together naturally through their shared history:
The Historical Link: Centuries ago, the cult of Tharizdun built a dark sanctuary in the Yatils to bring about world destruction. After a coalition of good forces defeated the cult and encased the temple in lead and magical wards, the location faded into obscurity. Later, Iggwilv established her lair in the Lost Caverns nearby, tapping into the lingering dark planar energies of the region to study demonology and write the Demonomicon.
The Overarching Plot:
Phase 1 (S4): The party ventures into the Lost Caverns to retrieve Iggwilv’s legendary hoard and neutralize the threat of her daughter, Drelnza.
Phase 2 (The Hook): Inside S4, the party discovers clues revealing that the dark power powering the caverns' defenses originates from an even older, sealed evil deeper in the mountains—the Forgotten Temple.
Phase 3 (W4): The party journeys to the Temple to prevent a resurgence of Tharizdun's cult, who are actively trying to break the ancient seals.
2. Linking the Modules in Gameplay
To seamlessly connect the two adventures, use one of the following transition methods:
Option A: The Direct Cavern Passage (Seamless Dungeon Crawl)
Mechanism: Create a hidden lower tunnel or sealed portal in the Lesser Caverns (S4 Level 1) or Greater Caverns (S4 Level 2).
Execution: After defeating Drelnza in S4's ultimate vault, the party finds a subterranean passage marked with the symbol of the Spiral of Decay (Tharizdun's holy symbol). Tying S4 directly to W4's lower/sub-basement level allows the party to progress without returning to town first.
Option B: Clues and Overland Journey (Two-Stage Campaign)
Mechanism: Place journals, maps, or artifacts in Iggwilv’s hoard detailing the Forgotten Temple.
Execution:
In Drelnza's tomb or the Treasury, include notes from Iggwilv describing how she siphoned energy from "The Sleeping Dark God."
Give the PCs a map showing the hidden valley of the Nchar (W4).
The party returns to town to rest and level up, then embarks on an wilderness trek through the dangerous Gnoll-infested valley leading to W4.
3. Structural & Pacing Adjustments
| Aspect | S4 Lost Caverns of Tsojcanth | W4 The Forgotten Temple of Tharizdun |
| Tone | Classic treasure hunt, magical mystery, high-fantasy monsters. | Cosmic horror, attrition, claustrophobic dread, cultic terror. |
| Primary Foes | Magical beasts, giants, Iggwilv's constructs, vampire (Drelnza). | Nchar/Gnolls, cultists, aboleths/undead, black cyst horror. |
| Target Levels | Levels 8–10 | Levels 9–11 (if played immediately after S4) |
Key Adjustments for the Combined Run:
Level Progression:
Start S4 at Level 7 or 8.
By the end of S4, PCs should reach Level 9 or 10.
Adjust W4's difficulty slightly upward if the PCs enter with high-tier magic items looted from S4.
Foreshadowing Tharizdun in S4:
Replace minor decorative motifs in S4 with images of black obelisks, jagged spirals, and sanity-warping inscriptions.
Give Drelnza or Iggwilv's lingering magic a subtle corrupting edge (e.g., strange nightmare visions during rests in the caverns).
Resource Management:
W4 is famous for its grueling siege mechanics and defensive monster positioning (particularly the valley and temple entrance guarded by nchar/gnolls). Ensure PCs have opportunities to rest or purchase supplies between the two modules if they choose Option B.
4. Key Clues & Narrative Seeds to Plant
The Black Cyst Fragment: Place a small, unidentifiable black obsidian fragment in Iggwilv's vault that radiates non-school magical aura. It acts as a key to the inner sanctum of W4.
Cultist Intercepts: Introduce a wandering band of Tharizdun cultists in the wilderness encounter table of S4 who carry orders to investigate the "neighboring caverns of the witch-mother."
The Artifact Link: If using the 333 Gem or other artifacts from S4, tie their creation to the siphoned power of Tharizdun's altar.
Combining S4 The Lost Caverns of Tsojcanth and W4 The Forgotten Temple of Tharizdun under the Adventurer Conqueror King System II (ACKS II) mechanics turns a classic dungeon crawl into a high-stakes campaign sandbox. ACKS II excels at wilderness exploration, domain governance, faction morale, and dynamic economic engines.
Integrating ACKS II shifts the campaign from a simple linear crawl into a strategic race across the Yatil Mountains against rival factions, cults, and local warlords.
1. ACKS II Campaign Framework & Domain Mechanics
Under ACKS II, the Yatil Mountains around the caverns and temple should be mapped as a Borderlands Hex Crawl anchored by a nearby civilization hub (e.g., a border fortress or march barony like Ghyrex or a Highfolk border outpost).
[ Base Town / Border Fort ]
│
├── (18-24 miles / 3-4 Hexes of Wilderness)
│
├──► [ S4: Lost Caverns of Tsojcanth ] (Level 6-8 Domain Threat)
│ │
│ └── Hidden Subterranean Path / Ancient Leyline
│ │
└───────────────────┴──► [ W4: Forgotten Temple of Tharizdun ] (Level 9-11 Cosmic Threat)
Domain Tier & Level Calibration
PCs Target Level: Levels 7 to 11 (Heroic to Name Tier).
Domain Management: At Level 9+, PCs start establishing strongholds, hideouts, or sanctums. Clearing out S4 or W4 gives them prime territory to secure a Mountain March or establish an Arcane Sanctuary.
Clearing & Securing Wilderness Hexes: S4 and W4 sit in un-cleared 6-mile wilderness hexes. To claim Iggwilv's former domain, the party must perform clearing operations (ACKS II Wilderness Clearing rules), driving out the wandering monster matrices (gnolls, giants, troglodytes).
2. Dynamic Faction Matrix (ACKS II Faction Rules)
Instead of static monster populations, run the Yatil region using ACKS II domain faction turns between delve sessions:
| Faction | Leader / Force | Domain Goals | ACKS II Alignment / Type |
| Cult of Tharizdun | Dark Bishop / High Priest | Unseal the Black Cyst under W4; capture S4's power nodes. | Chaos / Cult |
| Nchar Gnoll Tribes | Chieftain / Flind Warlord | Control the mountain passes; extract tribute from adventurers. | Chaos / Monster Horde |
| Local Barony / March | Border Margrave | Eliminate mountain threats; claim Iggwilv’s legendary hoard for coffers. | Law / Realm Domain |
| Vampire Drelnza's Cadre | Drelnza (S4 Vault) | Maintain dormancy, protect Iggwilv's treasures, corrupt nearby tribes. | Chaos / Undead Domain |
Faction Turn Actions
Cult Expansion: If the PCs delay after clearing S4, the Cult of Tharizdun sends a warband from W4 to occupy the cleared levels of S4 to siphon remaining magical nodes.
Troop Morale & Recruitment: The Gnoll tribes in W4 use ACKS II mercenary rules; if their leadership falls or morale breaks during a siege, surviving bands scatter or contract out as mercenaries.
3. ACKS II Mechanical & System Conversions
S4 & W4 Treasure Engine (Gold-to-XP)
ACKS II relies on gold-to-XP conversion ($1\text{ gp} = 1\text{ XP}$) balanced by strict carrying capacity (stone/items) and logistics.
S4 Hoard Riches: Iggwilv’s hoard is colossal. Transporting thousands of gold pieces, trade goods, and art objects out of the Yatil peaks requires hirelings, pack mules, and guard escorts.
Loot Logistics: Returning to base with 50,000 gp in coin requires 50 stones of capacity, forcing PCs to set up secure supply lines, leave guards at the cavern entrance, or hire mountain guides.
Sanity & Horror (Tharizdun’s Influence)
ACKS II handles dark magic via Mishaps, Curses, and morale checks. In W4:
Cosmic Dread: Resting within W4 requires a Hardiness / Saving Throw vs. Spells. Failure inflicts temporary fatigue or chaotic magical quirks (matching ACKS II Sinkhole of Evil rules).
Unholy Power Nodes: Cult Altar sites grant bonuses to Chaotic spells but require Lawful characters to make Morale/Loyalty checks if lingering too long.
Spells & Magical Research
Iggwilv’s lab in S4 serves as a functional ACKS II High-Level Laboratory:
Rogue mages/Mage-crafting PCs can use the library to research custom spells, manufacture magical items, or perform ritual demon-binding using ACKS II Arbitrary Magical Effects and Ritual Magic frameworks.
4. Combined Campaign Progression Flow
Phase 1: The Wilderness Hex-Crawl (Levels 7-8)
├─ Navigate dangerous Yatil Mountain hexes (Weather, Avalanches, Gnoll Patrols).
└─ Discover rumor hooks regarding Iggwilv's lost domain.
Phase 2: Delving S4 - The Lost Caverns (Levels 8-9)
├─ Tactical dungeon crawl through Lesser & Greater Caverns.
├─ Defeat Drelnza & secure Iggwilv's Hoard.
└─ Recover Clues/Key Artifacts to Tharizdun's dormant threat.
Phase 3: Domain Logistics & Warband Mobilization (Level 9-10)
├─ Transport loot back to civilization; recruit mercenaries and henchmen.
└─ Establish a forward camp/fortified outpost in the cleared S4 Hex.
Phase 4: Siege & Descent into W4 - The Forgotten Temple (Levels 10-11)
├─ Overcome W4's valley defenses (Gnoll/Nchar military encampment).
├─ Penetrate the sealed Temple & Sub-Basement levels.
└─ Confront the Cult, prevent the unsealing of the Black Cyst.
5. Sample ACKS II Encounter Table (Yatil Hexes)
When PCs travel between S4 and W4 (1d6 per 6-mile hex, encounter on 1-2):
| 2d6 | Encounter (ACKS II Format) | Notes / Faction Tie |
| 2 | Demon (Vrock/Hezrou) | Lingering guardian bound by Iggwilv; hostile to all. |
| 3-4 | 1d4 Tharizdun Zealots & 2d6 Cultists | En route to W4 carrying sacrifice; will attempt ambush. |
| 5-7 | 3d6 Gnoll Raiders (Nchar Tribe) | Scouting force; roll Morale check if leader killed. |
| 8-9 | 1d3 Mountain Giants / Hill Giants | Territorial neutral force; negotiable with bribe/food. |
| 10-11 | Rival Adventurer Party / Mercenaries | Seeking Iggwilv's hoard; potential allies or competitors. |
| 12 | Cosmic Anomaly / Dark Leyline Portal | ACKS II Sinkhole of Evil; distorts magic and time. |
