OD&D Monks in Chainmail Combat

25 Apr, 2026

The Monk class for the Original D&D¹ was introduced in Supplement II: Blackmoor.² Since by this point the usage of Chainmail³ combat system was phasing out, this class is presented exclusively for the "Alternate Hit Dice and Hit Point Accumulation" and "Alternate Combat System" additions/amendments from the Supplement I: Greyhawk.⁴ Let's see how hard it would be to backport this class to be compatible with the Chainmail mechanics.

Contents

• Hit Dice
• Fighting Capability
• Open Hand
• Adjusted Monk class

Hit Dice ↩

Despite being a Cleric subclass, Monks use d4 Hit Dice in the "Alternate Hit Dice and Hit Point Accumulation" system. Thus, it stands to reason to grant them the same HD progression as the Magic-Users, as theirs is also changed to a d4 one in the Supplement I: Greyhawk.⁴

Fighting Capability ↩

Since the monks are Clerics, let's use the same Fighting Capability for them as well. The original table stops at the 10th level, but the Greyhawk supplement expands it up to 20th — more than enough to satisfy our needs.

Open Hand ↩

Now, that is the most challenging part of the conversion. The original Open Hand attack progression contains the whole plethora of polyhedra (sans d20) and sometimes an uneven number of attacks per round:

Could it be changed to use d6 dice only, while maintaining roughly the same number of attacks and average damage output per round? Surprisingly, yes! We'll need to bring out the spreadsheet calc for this, though:

As you can see when comparing the OrigAvg and NewAvg columns, we can keep the average damage pretty much the same by sacrificing the precision in the minimum and maximum ranges. Here's a chart representing the difference between the two progressions:

Adjusted Monk class ↩

With all that in mind, our new Monk progression would look like this (keeping all other parameters the same as in the original version).

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