Converting Dave Hargrave’s The Arduin Grimoire Vol. II: Welcome to Skull Tower (1978) to Adventurer Conqueror King System II (ACKS II) involves bridging two very distinct Old-School Revival (OSR) philosophies.
Arduin was chaotic, gonzo, high-lethal, and rule-breaking (introducing hit location tables, high-damage criticals, multidimensional tech, and radical class variants).
ACKS II is a rigorously simulationist, economically balanced, and mathematically sound B/X-derived system.
Here is how to adapt the core concepts, mechanical quirks, and signature elements of Welcome to Skull Tower into ACKS II. This blog post picks right up from Integrating Adventurer Conqueror King System II (ACKS II) with the legendary, chaotic, and maximum-gonzo DNA of Dave Hargrave’s Arduin Grimoires - Arduin Caravan ACKS II rpg
1. Philosophical & System Translation Rules
| Arduin Concept | ACKS II Equivalent / Translation | Notes |
| Descending AC (AC 9 to AC -10) | Ascending AC (AC 0 = Naked, AC 2 = Leather, AC 7 = Plate + Shield) | Convert Arduin AC: $\text{ACKS AC} = 9 - \text{Arduin AC}$. |
| Attack Rolls (d20 vs Target AC) | Attack Throw (Target AC + Base Attack Throw) | Use standard ACKS II Attack Throw progressions (Fighter 11+, Mage 13+, etc.). |
| Saving Throws | ACKS II 5-Category Saving Throws | Map Arduin saves directly to Blast/Breath, Lethal, Poison, Spells, or Devices. |
| Extreme Critical Hits / Fumbles | Mortal Wounds & Severed Limbs | Map Arduin’s gruesome critical tables to the ACKS II Mortal Wounds Table. |
| Gonzo / Multiversal Loot | High-Value Relics / Shaded Artifacts | Assign high-tier GP value, or treat cross-genre items as ancient First Age artifacts. |
2. Converting Signature Arduin Classes to ACKS II
Welcome to Skull Tower introduced several memorable class concepts and variants. In ACKS II, you can implement these using the Custom Class Creation System from the ACKS II Judge's Journal.
The Rune Weaver (Arduin Arcane Class)
In Arduin, Rune Weavers carve runes into physical media to store and trigger spells.
ACKS II Implementation: Build as an Arcane Class with the Artifice / Inscription trade skill, or a specialized variant of the Mage.
Class Trade-offs: Reduce Hit Die to d4, grant standard Arcane spell casting, and grant the Rune Scribe custom proficiency (allowing the creation of spell scrolls, glyphs, and warding runes at half normal time and gold cost).
The Amazon Warrior
In Hargrave's rules, Amazons gained specific combat bonuses and martial prowess.
ACKS II Implementation: Build as a custom human class using the Fighter Archetype (d8 Hit Dice, standard combat progression).
Proficiencies: Grant Combat Reflexes, Running, and Weapon Focus (Bow or Spear).
3. Monster & Encounter Conversion
Arduin monsters are notoriously deadly, often featuring unusual special attacks or massive hit points.
Quick Conversion Matrix for Arduin Monsters
Hit Dice (HD): Keep the same HD count. Recalculate hit points using ACKS II HD standards (d8 for normal monsters).
Armor Class (AC): Convert using $\text{ACKS AC} = 9 - \text{Arduin AC}$.
Movement: Convert Arduin inches/feet to ACKS II turn/encounter speeds:
$9''$ or $90' \rightarrow 120'/40'$
$12''$ or $120' \rightarrow 150'/50'$
Morale: Map Arduin aggressiveness to the ACKS II d20 Morale scale (-4 to +4, where 0 is standard).
Example Monster Conversion: Skull Tower Phantasm
Arduin Stats (Vol. II): HD 6, AC 2, Damage 1d10 + Energy Drain, Speed 12'', Attacks: 2 Touches.
Phantasm (Undead Monster)
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Hit Dice: 6* (27 hp)
Armor Class: 7 (Ascending)
Attacks: 2 ghostly touches (+6 attack throw)
Damage: 1d8 + Energy Drain (1 level on failed save vs. Lethal)
Movement: 150' (50') flying
Saving Throws: 11+ (Blast 12+, Lethal 11+, Poison 11+, Spells 12+)
Morale: +2
XP Value: 1,070 XP
Special Abilities: Incorporeal (only hit by silver/magic weapons),
Undead immunities (sleep, charm, hold, poison).
4. Adapting Arduin Mechanics & Flavor
1. Critical Hits & Lethality
Arduin is famous for its brutal critical hit tables (e.g., "Skull crushed, brain destroyed instantly").
ACKS II Integration: Use the native ACKS II Mortal Wounds and Tampering with Mortality mechanics.
Optional "Gonzo" Rule: If a character suffers a critical hit, apply a -4 penalty to their roll on the ACKS II Mortal Wounds table to simulate Hargrave’s sheer lethality.
2. Treasure & Multi-Genre Artifacts
Welcome to Skull Tower often intermingles classic medieval fantasy loot with high-tech or alien items (laser pistols, power cells, alien artifacts).
ACKS II Integration:
Classify high-tech items as First Age Artifacts or Chthonic Devices.
Assign a Gold Piece Value (GP) based on utility to ensure it integrates seamlessly into ACKS II’s campaign economy and XP progression.
Require a Proficiency Check (Engineering or Ancient History) to operate high-tech devices without causing a catastrophic malfunction.
3. Dungeon Delving in Skull Tower
Dungeon Mechanics: Map Arduin dungeon levels using the ACKS II Dungeon Exploration Engine (turns, wandering monster rolls every 2 turns on a d6, light management, and encumbrance by stones/weight).
Traps: Convert Arduin traps directly to ACKS II Save vs. Blast/Breath or Lethal, dealing damage scaled by dungeon level:
Level 1-2: 1d6–2d6 damage
Level 3-5: 3d6–6d6 damage
Level 6+: 8d6+ damage or save-or-die / save-or-maim
One of the most terrifyingly iconic creatures to come out of Dave Hargrave’s Arduin Grimoire trilogy (Welcome to Skull Tower) is the Hell Maiden.
Appearing as statuesque, metal-clad warrior women whose heads are bare, grinning animal-and-humanoid skulls, Hell Maidens are not undead—they are extraplanar, flesh-eating warrior demonesses that ride skeletal steeds (Hell Horses) into combat, collecting the slain to bring back to their dark realms.
Here is a complete ACKS II stat block and tactical encounter guide for translating a Hell Maiden into your campaign.
Hell Maiden (Monster Stat Block)
From the front, she appears as a knight in burnished obsidian plate armor, wielding a heavy lance. When her visor lifts, there is no face—only a polished, bone-white human skull emitting a low, vibrating screech.
Hell Maiden (Extraplanar / Demonic)
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Hit Dice: 7* (31 hp)
Armor Class: 8 (Plate Armor + Shield, Ascending)
Attacks: 1 Heavy Lance (+7 attack throw, 1d10+2 damage / 2d10+4 mounted charge)
OR 1 Broadsword (+7 attack throw, 1d8+2 damage)
Movement: 120' (40') / Mounted: 240' (80')
Saving Throws: 10+ (Blast 11+, Lethal 10+, Poison 10+, Spells 11+)
Morale: +2
Alignment: Chaotic
XP Value: 1,250 XP
Number Appearing: 1d4 (Lair: 2d4)
Special Abilities: Demon-Skin, War Screech, Death-Grasp, Planar Sight.
Special Abilities
Demon-Skin: Non-magical weapons bounce off a Hell Maiden without dealing damage. They can only be harmed by magical or silver weapons. Despite their skeletal appearance, they are not undead and cannot be Turned by Clerics.
War Screech: Once per encounter, a Hell Maiden can emit a terrifying, unnatural war cry. All enemies within 60 feet must make a Save vs. Spells or suffer a -2 penalty to Attack Throws and Morale checks for 1d6 rounds due to sheer dread.
Death-Grasp: If a Hell Maiden reduces a PC to 0 HP with a melee attack, the target immediately suffers a -2 penalty on their ACKS II Mortal Wounds Table roll. If the PC dies, the Hell Maiden will attempt to sling the corpse over her mount as a trophy/food source.
Immunity: Completely immune to level/energy drain, sleep, charm, hold, and fear effects.
The Mount: Hell Horse
Hell Maidens rarely travel on foot. They ride Hell Horses—skeletal equines with cat-like fangs, bone-hooves, and burning green flames inside their eye sockets.
Hell Horse (Undead Beast)
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Hit Dice: 5* (22 hp)
Armor Class: 5 (Ascending)
Attacks: 2 Hooves (+5 attack throw, 1d6 damage) and 1 Bite (+5 attack throw, 1d8 damage)
Movement: 240' (80')
Saving Throws: 12+
Morale: +3 (+4 if rider is present)
Alignment: Chaotic
XP Value: 425 XP
Special Abilities: Undead Immunities, Silver/Magic to Hit, Anti-Dwarf Fury.
Anti-Dwarf Fury: Hell Horses harbor a deep, magical hatred for Dwarves. If a Dwarf is present in the party, the Hell Horse will always target them first in combat unless forced otherwise by its rider.
Encounter Guide: The Black Tollbridge
Scenario Setup
The PCs are traveling through a wilderness choke point (a narrow canyon pass, an ancient stone bridge over a chasm, or a ruined watchtower threshold). A solitary Hell Maiden mounted on a Hell Horse stands motionless, blocking the path. A heavy iron cage dangles from her saddle, holding the bloodied remnants of a previous adventuring group.
Tactics & Behavior
The Charge (Round 1): If the PCs approach aggressively, the Hell Maiden uses her movement to initiate a Mounted Charge with her heavy lance (+7 to hit, dealing 2d10+4 damage).
The Shockwave (Round 2): After the initial charge, she wheels her mount around and uses her War Screech to break party cohesion and force Morale checks on hirelings/henchmen.
Flanking & Isolation (Round 3+): She uses the mobility of her Hell Horse to isolate squishy targets (Mages, Thieves) or direct her mount toward any Dwarves in the front line.
She switches to her broadsword for close-quarters fighting. Retreat Condition: A Hell Maiden's goal is hunting, not suicide. If her mount is slain or she is reduced to under 25% HP, she will attempt to grab a fallen party member or corpse and escape into the Ethereal Plane / Outer Dimensions (taking 1 turn to channel).
Loot & Campaign Economy (ACKS II Integration)
Defeating a Hell Maiden yields high-tier loot, but requires handling cross-planar materials carefully:
Obsidian Plate Armor of the Void: Fits only Chaotic humanoids or extraplanar beings. Can be re-forged by an expert armorer (requiring 1,000 GP in labor) into standard +1 Plate Armor for a PC.
Demon-Steel Broadsword: Counts as a magical weapon (+0 to hit, but bypasses damage resistance requiring magic weapons). Worth 1,200 GP to collectors or sages.
Loot Bag / Saddlebags: Contains 2d6 $\times$ 100 GP in trade gems, 1d4 healing potions stolen from past victims, and potentially a First Age Artifact or strange planar device (e.g., an alien compass that points toward multidimensional rifts).
