Running The Age of Conan with OD&D and Chainmail

03 Aug, 2025

Following the playtest of the Bossonian Marches, here is a collection of notes and thoughts regarding running the game of OD&D+Chainmail.

Contents

• Ruleset
• Weather
• Morale
• Spell Complexity
• Counter-spell
• 2d6 for everything
• Shooting into Melee
• Withdrawing from Melee
• Man-to-Man Combat
• Conclusion

Ruleset ↩

Here's a list of books that were used in general priority of the rules:

1. The three Age of Conan booklets¹
2. The three original Dungeons & Dragons booklets²
3. Chainmail³ with minor inclusions from Swords & Spells⁴ covering the missing rules
4. Parts of Greyhawk,⁵ Blackmoor,⁶ and Eldritch Wizardry⁷ supplements for select classes and monster statistics

Weather ↩

The optional "Weather" rule from Chainmail is great to determine weather while traversing the wilderness, though the suggested frequency of checking (every other turn) is too fast even if you use the D&D's 10-minute turns instead of the Chainmail's 1-minute ones. For our game, we decided to roll for a weather change twice per day instead.

^* ×2 fatigue, greater chance of wildfire.

^† 3 turns of hard rain bring mud, halving the movement.

Morale ↩

While morale is mentioned in the D&D booklets, the rule itself is absent there and must be taken from Chainmail. An important note considering the morale ratings stated in the Chainmail's "Fantasy Supplement" are for use with the "Post Melee Morale", NOT the optional "Morale: Instability Due to Excess Casualties" rule. What's interesting is that the latter "equal or better on 2d6" rule was probably the precursor for the more widely known "under or equal on 2d6" (or 2d10 in case of AD&D) morale system.

Spell Complexity ↩

One of the peculiarities of the Age of Conan supplement is its employment of Chainmail's "Spell Complexity" checks for casting spells, the outcome being the spell cast "I"mmediately, be "D"elayed, or "N"egated entirely if the roll the stated value or less. This system also allows for the possibility of ritually (10 minutes per spell level) casting spells from scrolls of levels higher than the caster can prepare.

The Chainmail has five "tiers" of spell casters, from the lowest to the most powerful ones: Seer, Magician, Warlock, Sorcerer, and Wizard. These terms were used later as class titles for the Magic-User. The Age of Conan shuffles them a bit for its Sorcerer class that replaces both Magic-Users and Clerics in the setting. If you want to use the Spell Complexity rule for the classic Magic-Users (and maybe even Clerics), you should decide how you would adapt this table to their level progression, as the aforementioned class titles are spread far more unevenly in the original rules — the following table demonstrates this problem. The "Draft" column is for the draft version of the rules from the Arneson vs. Gygax lawsuit scans.⁸

Yet another logical approach is to untie the tiers from the class titles, aligning them with the maximum available spell level instead. With this done, after extrapolating the table to the 9 spell levels, and after fixing some apparent typos (inspect Warlock Complexity Value 2 in the original), the table takes the following form:

Counter-spell ↩

Another interesting Chainmail rule is the possibility of one Magic-User to counter the other ones' spell:

The stronger magician can successfully cast a counter-spell with a two dice score of 7 or better, while a weaker magician needs a score of 8, 9, 10 or 11, depending on his relative strength. A counter-spell fully occupies a magician's powers.

This could be represented more clearly with the following table (note that the titles are from Chainmail):

If we instead used the maximum available spell level as we did with Spell Complexity above, the table would look as follows:

Another possible (and simpler) approach is for the target number to be 7 plus half the difference (rounded down) between the level of the opposing Magic-User and yours.

2d6 for everything ↩

Another idea we have tested in this game was the "d6-only" mechanics, meaning converting all d20 (Saving Throws) and d100 (Thieving Skills) rolls to 2d6. There isn't much reason to do so except you don't have anything except a bunch of six-siders handy, but it was still fun to try out. The Age of Conan presents its own unified 2d6 Saving Throw mechanic, but I wanted to keep the classic five categories.

Through the intermediate conversion to percentile chances, the Saving Throws can be quite closely converted to 2d6, the maximum deviation varying from −3 to +8 percent chance of success with the median of +3%.

d20 <-> 2d6 reference:

A similar conversion method was used with the percentile rolls.

d100 <-> 2d6 reference:

Shooting into Melee ↩

Players yearn for shooting into melee. One of the first issues that arose during play was the inability to target enemies engaged in melee combat. It sounds perfectly fine for the default 1:20 battle scale in Chainmail, but it's a nice option to have on the 1:1 scale.

After some discussion, we have decided on the following house rule:

Shooting into Melee: You can target an enemy engaged in melee with a −2 penalty to hit. If you miss, the actual target is chosen randomly from those engaged in the same melee, be they friend or foe. Check if you hit the new target using the original roll without the −2 penalty.

If you want to do this in mass combat, you can employ the rule from Swords & Spells⁴:

Missile Fire into Melees: Firing into melees is permitted, with damage divided proportionally into hostile and friendly figures. Large figures that protrude or are otherwise exposed can be fired at with no penalty.

In addition to that, we modified the Chainmail rules for cover and aiming that were originally used for the firearms for general use with all missile weapons:

Missile Modifirers for the Man-to-Man Combat:

• soft cover reduces direct missile damage by one-half (rounded down);
• the target is up to ½ behind hard cover: −1 penalty to hit;
• the target is over 1½ behind hard cover: −2 penalty to hit;
• spending a round standing still to carefully aim grants a +1 bonus to hit for a single shot.

Withdrawing from Melee ↩

A rule that is not explicitly present in Chainmail, except for backing/retreating due to a Post Melee Morale check, but a pretty important at a 1:1 scale in the Man-to-Man Combat. This can be fixed with this addition:

Disengaging from Melee: After the first round of melee, on their move phase, figures can choose to:

• Withdraw, moving back up to ½ move facing the enemy. If the enemy figures are able to follow, they can do so at the end of the current movement phase.*
• Retreat up to 1 move with backs to the enemy, according to the Retreat and Rout rule.

* This ensures that figures withdrawing at the last movement phase won't immediately fire back at the missile phase.

Man-to-Man Combat ↩

Man-to-Man rules turned out quite good, at least on the lower levels (we have played up to about the 3rd). The different chances to hit a certain armor type, as well as the order of attacks on the first and subsequent rounds, depending on the weapon length and speed, are quite engaging and make weapon choice matter despite all the weapons dealing d6 damage.

Instead of the chances to hit increasing with gaining new levels (like in the d20 system), you raise the number of attacks per melee round. One concern I have is that once the number of attacks per round rises high enough, the combat will proportionally slow down. This will make the Troop Type system more manageable against a large number of low HD foes.

The main factor that makes Man-to-Man Combat slower is that you cannot throw your attacks all at once (as you do with the Troop Type system), since you need to throw a pair of dice for each one. I can see a couple of potential ways to mitigate the problem, each with its pros and cons:

1. Use the Troop Type system for most battles, saving the Man-to-Man Combat for challenging duels and boss battles.

• Pros: Extremely fast and simple.
• Cons: Lower resolution scale — all your characters become one of the three types of "Foot" troops in attack and defense.

2. Convert the Man-to-Man table to d20.

• Pros: Keeps the intricacies of weapon-vs-armor interactions.
• Cons: No bell curve distribution; magic bonuses are diminished due to the higher range of values.

3. Roll d12 instead of 2d6.

• Pros: Same as with (2), but no need for conversion, keeping the same range of values.
• Cons: Still no bell curve distribution.

Using Man-to-Man Combat with non-humanoid monsters is also possible, but you'll need to figure out which type of armor they have and what weapon can most closely represent their attacks. The latter is mostly arbitrary, while the former is pretty straightforward:

Conclusion ↩

Overall, I consider this test to be a success. We had cleared the main dungeon and about half of the second one, finishing with a short mass combat skirmish in the swamp. The system had proved to be quite robust, though nevertheless, it still needs filling in the blanks here and there. Plans for the next time include more Troop Type battles and Fantasy Combat encounters, or even substituting the Fantasy Combat table with the "Alternative Combat System", as was suggested in the draft version⁹ of the original rules.

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