So a couple of years ago I ran an Amazing Adventures Halloween special one shot with eight player's PCs making a raid on Hell erm the Infernum! This was to free a cohort who'd gotten themselves taken to Advenus. But how does one combined Amazing Adventures, the D20 Infernum and The Nine Hells, Part 1 & 2 by Ed Greenwood from Dragon magazine issue 75?!
Yes, Amazing Adventures can be played with Infernum, but it requires some straightforward system conversion.
Because both games share a common heritage in the Open Game License (OGL) and d20-style design, they are fundamentally compatible in concept. However, they use slightly different core mechanical frameworks.
Understanding the Mechanics Gap
Infernum (Mongoose Publishing): Built directly on the standard d20 System / D&D 3.5e OGL framework.
It uses traditional Armor Class (AC), Base Attack Bonus (BAB), standard skill points, and fixed Saving Throws (Fortitude, Reflex, Will) tied to 3.5e mechanics. Amazing Adventures (Troll Lord Games): Built on the SIEGE Engine (the same system powering Castles & Crusades).
While it retains the core six ability scores, d20 attack rolls, and AC, it streamlines skill checks and saves into unified SIEGE Checks (Target Number 12 for Prime Attributes, 18 for Non-Prime).
How to Blend or Convert Them
Depending on which direction you want to run the game, conversion is generally low-effort:
Option 1: Running Infernum Content using Amazing Adventures (Recommended)
If you want to use Amazing Adventures as your primary chassis to run a dark, infernal campaign setting:
Monster & Demon Stat Blocks: Use the AC, Hit Dice (HD), hit points, and base attack values from Infernum directly. To adapt special abilities or spells, assign them a Challenge Level (CL) equal to the creature's HD and require a standard SIEGE Check.
Saving Throws: Convert Infernum's Fort/Reflex/Will saves into SIEGE Checks based on the corresponding ability score (Strength/Con for Fort, Dex for Reflex, Wis/Cha for Will).
Mutations & Hellfire Guns: You can port Infernum’s mutations and firearms directly over as gear, traits, or cyberware/gadgetry using Amazing Adventures’ gadget/powers rules or simply keeping their flat damage dice.
Option 2: Porting Amazing Adventures Classes into Infernum (3.5e Engine)
If you prefer to run the crunchy 3.5e/d20 ruleset of Infernum:
Convert the Amazing Adventures classes by giving them standard d20 Base Attack Bonus progressions (Full, 3/4, or 1/2) and standard 3.5e Save progressions (Good vs. Poor).
Convert SIEGE-based class abilities into standard d20 skill bonuses or feats.
Synergy & Tone
Thematically, the two games pair exceptionally well:
Dark Fantasy & Weird Science: Amazing Adventures handles multi-genre pulps, occult investigation, and modern/sci-fi action seamlessly.
Grim & Mutated Settings: Infernum brings dark fantasy horror, biomechanical demonic technology, demonic covenants, and mutations.
Using Amazing Adventures as the engine helps strip away the heavy crunch and book-keeping of 3.5e while allowing you to tap into Infernum's deep lore, dark tech, and hellish campaign settings.
Integrating Ed Greenwood’s seminal article "The Nine Hells, Part 1" (from Dragon Magazine #75, July 1983) into Mongoose Publishing's Infernum RPG (the Book of the Damned, Book of the Tormentors, and Book of the Conquerors) provides a rich blend of classic AD&D outer-planar hierarchy and Infernum’s dark biomechanical, pit-borne ecosystem.
Conceptual Alignment
The Classical Hell vs. The Infernum Pit: Greenwood's Dragon #75 establishes the upper layers of Hell (Avernus, Dis, Minauros, Phlegethos) as structured, feudal domains populated by unique lesser/greater devils, marshaling areas for invasion, and iron citadels.
Infernum treats Hell as a living, flesh-and-metal abyss governed by ancient Great Houses (e.g., Astyna, Malphas, Zeth) contending for power and resources. The Bridge: Greenwood’s lesser unique devils (such as Nergal, Arioch, Biffant, and Bist) become Outcast Warlords or Pre-Sunder House Patriarchs in Infernum, operating outside the main House hierarchy or holding volatile boundary fiefdoms in the upper reaches of the Pit.
Step-by-Step Integration into the Infernum Core Trilogy
1. Integration into Book of the Damned (World & Lore)
Avernus as the Staging Grounds: In Greenwood's article, Avernus serves as a barren, craggy wasteland and training ground for infernal legions.
In Infernum, integrate Avernus as the Upper Marches or the outermost skin of the Pit—a staging ground where House legions (such as House Astyna’s drop-forces or House Zeth’s siege engines) conduct military drills and ambush planar trespassers. Lesser Unique Devils as Free Agents: Greenwood details non-archdevil entities like Nergal (the lion-headed, toad-like horror) and Arioch. In Infernum, treat these beings as Engineered Primordials or Free-Agent Warlords who refuse to swear fealty to any single House, maintaining secret armories and treasure grottos across the upper crags.
2. Integration into Book of the Tormentors (Demons, Mutations, & Mechanics)
Biological Mutations & Hellfire Guns:
Convert Greenwood's lesser unique devils into high-HD Demon Stat Blocks using Infernum’s Sinner/Demon Creation rules.
Give Nergal the Oozing Poison/Corrosive Secretion mutation to represent his toxic, sore-covered skin.
Equipment: Equip these classic devils with Infernum’s bio-mechanical technology, such as Hellfire Artillery, Agony Needlers, or Flesh-fused Armor.
Environmental Rules:
Greenwood’s environmental hazards (burning sands, ambient planar darkness, iron dust storms) directly map to Infernum’s Pit Hazard Tables. Treat Avernus and Dis as high-radiation/high-heat ambient zones requiring Fortitude saves or environmental shielding.
3. Integration into Book of the Conquerors (House Warfare & Domain Management)
Faction Matrices & Fiefdoms:
Use Greenwood's feudal hierarchy (dukes, counts, marshals) to construct a custom Minor House or Renegade Faction Matrix using Book of the Conquerors’ domain rules.
Assign Greenwood's lesser devils specific land holdings (e.g., Biffant operating as a diplomatic ambassador or administrator within a rival House’s capital).
Covenant & Soul Mechanics:
Integrate Greenwood’s rules for soul-harvesting and lemure exploitation into Infernum’s Husk/Soul Economy, allowing player-characters or rival lords to vie for control of Avernus's soul-funnels.
Comparative Conversion Summary
| Feature in Dragon #75 | Infernum Equivalent | Conversion / Placement Strategy |
| Avernus (Layer 1) | The Upper Marches / Outer Skin | Staging ground for House invasions and scavenger fiefs. |
| Lesser Unique Devils (Nergal, Arioch) | Unaligned Warlords / Primordial Demons | High-level NPC bosses with unique mutation profiles and biomechanical gear. |
| Iron City of Dis (Layer 2) | House Zeth Heavy Industrial Spire | A massive forge-citadel manufacturing Hellfire weapons and cybernetics. |
| Feudal Dukes & Marshals | House Aristocracy / Covenant Lords | Domain rulers managed via Book of the Conquerors faction mechanics. |
Integrating Ed Greenwood’s two-part masterpiece "The Nine Hells" (from Dragon Magazine #75 and #76, July/August 1983) into Mongoose Publishing’s Infernum RPG trilogy—Book of the Damned, Book of the Tormentors, and Book of the Conquerors—creates an extraordinary fusion.
It bridges AD&D's iconic, highly bureaucratic outer-planar hierarchy with Infernum’s dark, bio-mechanical, pit-borne ecosystem of warring Houses and mutated fiends.
World Synthesis: The Classic Hells as the Pit's Strata
Greenwood's two-part article provided a comprehensive breakdown of Hell's geography, planar magic rules, lesser/greater unique devils, and the internal politics of the Archdevils.
In Infernum, the Pit is an endless, living biomechanical vertical abyss divided into distinct depths. We map Greenwood's 9 Layers to the structural depths of Infernum:
The Upper Marches (Avernus & Dis): The outer, heavily industrial crust. Dis becomes the primary stronghold of heavy military Houses (like House Zeth), churning out Hellfire siege machinery and bio-armor.
The Mid-Depths (Minauros, Phlegethos, Stygia, Malbolge): The volatile regional fiefdoms.
Minauros’ sinking mud pits and Stygia’s frozen expanses represent corrupted, climate-shifting biomes caused by broken Pit engines and unstable Earth-Currents. The Deep Abyss (Maladomini, Cania, Nessus): The ancient core where the House Patriarchs, primordial devils, and ancient pit structures reside.
1. Integration into Book of the Damned (Lore & Environment)
Planar Mechanics & Environmental Hazards: Greenwood’s articles introduced specific rules for environmental survival and altered spellcasting across the Nine Layers. In Book of the Damned, translate these into Pit Hazard Tables:
Avernus Fireball Storms & Dis Iron Heat: Modeled as ambient heat/fire radiation requiring environmental shielding or Fortitude/Con-based SIEGE saves.
Alteration of Magic: Greenwood’s restrictions on planar magic map directly to Infernum’s Sickness/Corruption of the Ether, where non-infernal spells require additional spell-point costs or provoke wild mutation rolls.
The Lesser Unique Nobles: Entities like Nergal, Arioch, Biffant, and Bist become Outcast Warlords or Pre-Sunder Primordials who refuse fealty to the Great Houses, operating in the lawless reaches between House territories.
2. Integration into Book of the Tormentors (Bestiary & Mutations)
Adapting Greenwood’s Unique Devils: Greenwood detailed dozens of unique lesser and greater devils with distinct physical descriptions and powers.
Use Book of the Tormentors’ Demon Creation & Mutation Rules to build them: Nergal: Give him the Corrosive Secretions and Amphibious/Pustule mutations to reflect his toad-like, sore-covered form. Equip him with heavy bio-artillery.
Arioch: Build with the Beast-Head (Reptilian), Flight (Bat Wings), and Titanic Strength mutations.
Infernal Technology Upgrades: Replace classical AD&D magic weapons held by Greenwood’s marshals with Infernum’s biomechanical arsenal:
Give Duke commanders Hellfire Cannons, Agony Needlers, and Bone-fused Cybernetics.
Lemures and Spined Devils are treated as low-tier Husks or Sinner Stock processed by House flesh-farms.
3. Integration into Book of the Conquerors (House Warfare & Domain Management)
Converting Feudal Dukes into House Matrices: Greenwood structured Hell like a complex feudal court filled with marshals, dukes, and competing lieutenants. Book of the Conquerors is built specifically for running House domains, fiefs, and military campaigns.
The Archdevils (Dispater, Mammon, Belial, etc.): Treat them as High Councilors or Founding Patriarchs of rival Great Houses.
The Feudal Lieutenants: Assign Greenwood's lesser court devils as Vassal Lords, Warmasters, or Spymasters within the Book of the Conquerors domain rules.
The Covenant & Soul Economy: Greenwood’s mechanics for soul harvesting and lemure distribution feed directly into Infernum’s Soul-Harvesting and Husk Infrastructure. Players managing a domain can build extraction engines on Avernus or run trade routes through Dis to fuel their military machine.
Quick Mechanical Conversion Guide
| Feature from Dragon #75/76 | Infernum System Equivalent | Conversion Rule / Adjustment |
| Layer-Specific Magic Penalties | Ether Mutation / Pit Distortion | Increases spell failure chance; triggers minor physical mutations on failure. |
| Unique Lesser Devils | Mutated Primordials / Outcast Lords | Generated using Book of the Tormentors Mutation Point budget based on HD. |
| Infernal Courts & Dukes | Great House Faction Matrix | Plug directly into Book of the Conquerors Domain & Influence Point mechanics. |
| Soul-Pits & Lemure Fields | Husk Processing Plants | Serves as the primary resource node for generating House soldier stock. |
