Wednesday, April 15, 2026

OSR Commentary Adapting I2: Dwellers In The Forbidden City by David Cook To The Barrows & Borderlands Rpg

 Adapting David Cook’s 1981 classic I2: Dwellers of the Forbidden City for a modern, grit-forward system like Barrows & Borderlands (B&B) requires shifting the focus from "heroic monster-slaying" to "tactical survival and factional maneuvering." This blog post picks right up from 

OSR Commentary Adapting C1: The Hidden Shrine of Tamoachan To The Barrows & Borderlands Rpg

The Forbidden City is essentially a "megadungeon" turned inside out. Here is how to translate its pulpy, lost-world atmosphere into the mechanical rigors of B&B.


1. The Core Atmosphere: Decay & Resource Scarcity

In B&B, inventory slots and light sources are life. The Forbidden City shouldn't just be "hidden"—it should be a resource sink.

  • The Jungle Trek: Treat the journey to the city as a series of Navigation Checks. Failure doesn't just mean getting lost; it means losing Rations or taking Fatigue levels before even reaching the gates.

  • Verticality: The city is a massive crater. Use B&B’s climbing and encumbrance rules to make descending into the city a literal "point of no return."

2. Faction Warfare (The Social Engine)

The strength of I2 is the three-way war between the Bugbears, Mongrelfolk, and Yuan-ti. In B&B, combat is deadly, so players should be encouraged to use the Reaction Table.

FactionB&B ArchetypeDispositionHook
MongrelfolkScavengers / OutcastsSkittishWill trade secrets for "pure" food or scrap metal.
BugbearsHeavy InfantryAggressiveLooking for "conscripts" (meat shields) for their next raid.
Yuan-tiEldritch CultistsManipulativeWill offer "blessings" (mutations) in exchange for live sacrifices.

3. Mechanical Conversions

B&B usually scales lower than AD&D. To keep the "Forbidden" feel, monsters should be dangerous but predictable in their behaviors.

The Yuan-ti (The Apex Predators)

Don't just give them high HP. Give them Special Abilities that interact with B&B’s conditions:

  • Hypnotic Gaze: Target must make a Will Save or be Stunned for 1 round.

  • Toxic Blood: If a Yuan-ti takes Slashing damage, adjacent players must check vs. Poison or take 1d4 damage.

The Tasloi (The Nuisance)

These should be B&B "Minions." They don't do much damage, but they excel at Stealing Items. Have them target a player’s "Utility Slot" (potions, torches) rather than their HP.


4. Hazard & Exploration Tweaks

The environment is as much an enemy as the inhabitants.

  • The Great Swamp: Movement is halved. Any roll of a "Natural 1" on an attack or dodge results in being Mired (requires a Strength check to move).

  • The Horrors in the Pits: Use the Ablative Armor rules for creatures like the Aboleth or Pan Lung (the oriental dragon). Players shouldn't be able to "swing" their way through these; they need to find environmental weaknesses.


5. Loot & Treasure

B&B focuses on "Wealth vs. Weight."

  • The Yuan-ti Hoard: Instead of just "1,000 gold," describe it as Heavy Golden Idols. They are worth a fortune but take up 3 slots each and impose a penalty on Stealth checks due to clinking.

  • Ancient Tech: Treat any found magic items as Relics with limited charges. Once they're gone, the item becomes a "Curiosity" worth gold but no longer functional.

GM Tip: The "Forbidden City" functions best when the players feel like they are caught in a pressure cooker. Keep track of Time Turns. Every hour spent debating is another chance for a rival faction's hunting party to find them.


  

Since you’re leaning into the lethality, we need to ensure the climax at the Temple of the Yuan-ti feels like a "survival horror" event rather than a fair fight. In Barrows & Borderlands, a lethal boss isn't just a bag of hit points; it’s a force of nature that requires the players to sacrifice resources or limbs to survive.

Here is how to tune the final encounter for maximum tension.


The "Final Boss": The Yuan-ti Abomination

In the original module, this is often a high-level priest. For a lethal B&B conversion, we’ll treat it as a Lesser Horror.

Stats & Dread Logic

  • Aura of Cold Blood: Any PC starting their turn within 10ft must pass a Will Save or take a penalty to their next Attack roll as their lizard-brain triggers a freeze response.

  • Multi-Attack: The Abomination attacks twice: once with a Scimitar (1d8+2) and once with a Constrict (see below).

The "Constrict" Mechanic (The Death Spiral)

If the Abomination hits with its tail, the player is Grappled.

  • Automatic Damage: The player takes 1d6 crushing damage at the start of every turn.

  • Resource Loss: To represent the ribs cracking, the player must choose: take an extra 1d6 damage OR permanently destroy one item in their Inventory Slots (shield shatters, potion vials break, etc.).


Environmental Hazards: The Sacrificial Pit

The fight shouldn't take place on a flat floor. The Temple is crumbling.

  • Slippery Blood/Oil: The floor around the altar is "Difficult Terrain." Any Dash action requires a Dexterity Check or the player falls Prone, granting the Yuan-ti Advantage on its next strike.

  • The Snaking Pillars: The Abomination can use its move action to vanish into the rafters. If the players lose sight of it, the next attack is a Surprise Attack (likely targeting the character with the lowest Armor).


The "Hard Choice" Victory

To make it feel like an authentic old-school module, give the players a way to win that doesn't involve "bonking it until it dies," but comes at a high cost:

The SacrificeThe Mechanical Result
Topple the Great IdolRequires 2 players to spend their full turn. Crushes the boss for massive damage but collapses the exit, forcing a dangerous escape through the "Unexplored Tunnels."
Ignite the Swamp GasIf players have a torch, they can ignite the vents. Deals 3d6 AOE damage to everyone. The boss dies, but players must check for Permanent Scars/Burns.
Offer a Blood DebtA player can "Accept the Mark." The boss stops attacking, but that player now has a Yuan-ti Taint, suffering a permanent penalty to Charisma and a future plot hook.

Implementation Advice

Note: Do not hide the lethality. Describe the "piles of bleached adventurer bones" and the "unnatural speed" of the creature. In B&B, players should only engage in a lethal boss fight if they’ve failed to find a clever way to bypass it—or if they are desperate for the loot.


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