Archive for June 10th, 2011


experimental combat system

Quick post because I have to get to work.

Several months ago I was wondering about how to separate deflection-type protection (shields, dexterity) from soak-type protection (armor).

In cases of uncertainty, the baseline here is the Moldvay/Mentzer Basic D&D combat system.

  1. Typical combat sequence is unaltered. Variable weapon damage is used.
  2. Attack rolls are made as usual in D&D: 1d20 + (class attack bonus/THAC0 stuff) + (ability mod) + (magic mod) + (circumstance)
  3. Ascending Deflection Class = 11 + (Dex mod) + (shield & shield magic mods) + (circumstance). Note: no actual “armor” in this calculation.
  4. If the attack roll equals or exceeds your deflection, guess what – you’re hit.
  5. If hit, Armor decreases the size of the damage dice: 1d10 > 1d8 > 1d6 > 1d4 > 2 > 1. Any hit does at least 1 point of damage, regardless.
  6. Multiple dice-types (3dX for example) shed the extra dice first, and once they hit 1dX then degrade to the lower dice type.  So 2d6 > 1d6 > 1d4.
  7. Light armor reduces the damage die type by one step, medium armor by two steps, and heavy armor by three steps.
  8. Damage is then rolled “normally” – the modifed die type + (ability mod) + (magic mod) + (circumstance)
  9. Magical armor lightens your Encumbrance Category, e.g., a heavily laden warrior in Plate +3 moves as if totally unencumbered.
  10. Monsters don’t have to be changed, but they could be depending on your ambition. An attack doing 1d3 damage reduces to 2 points, not 1.

Thus: Arnold Littleworth, under this system, has a Bathrobe of AC 4, which is equal to Chain + Shield. His Deflection class is 11 (base) -1 (poor Dexterity) +1 (equivalent to shield) = 11.

If, solely for the sake of science, Martin le Black attacked Arnold with his +2 sword Bazilien, his attack roll would be executed normally, hoping for a roll equal or better than 11. Because Arnold’s Bathrobe is equivalent to Chain armor, the damage from Bazilien would be 1d4 (starting from 1d8 and reducing two steps) +1 (strength) +2 (magic).

Action Normal B/X D&D Experimental System
Martin hits Arnold … 60% of the time 80% of the time
On average Martin inflicts 7.5 damage 5.5 damage
Expected damage per round 4.5 damage 4.4 damage

Note a couple of effects from this experimental system:

  • Armor reduces damage, it doesn’t keep you from getting hit in the first place.
  • Magic-Users and Clerics can make “touch attacks” to overcome Deflection Class much easier than AC
  • Characters are hit more often for less damage. Armor is approximately twice as useful as before, which helps Level 1 wimp-o’s.
  • Damage reduction is neither fixed nor does it require an extra roll, i.e., it’s unpredictable without slowing play
  • Against a guy with heavy armor, a dagger +1 does the same damage as a normal sword (more, on average, since it hits more often): magic is cool
  • Heavily armored knights are slow and easy to hit, but very difficult to wound without magic.
  • The special thing about Frodo’s undershirt is that it was extremely lightweight and easily concealed – like not wearing armor at all.
  • Maybe someone other than me will enjoy the strategic effects of Encumbrance… oh who am I kidding

Just to see what it would look like, here is the comparison for a duel between Martin le Black and Hanna Darrowkin, using their stats as of 1/9/2011:

Action Normal B/X D&D Experimental System
Martin hits Hanna … 25% of the time 55% of the time
On average Martin inflicts 7.5 damage 5 damage
Expected damage per round 1.875 damage 2.75 damage
Action Normal B/X D&D Experimental System
Hanna hits Martin … 30% of the time 60% of the time
On average Hanna inflicts 3.5 damage 1 damage
Expected damage per round 1.05 damage 0.6 damage

What’s happening here is that Hanna, physically weaker, is using what amounts to an ordinary sword to attack a stronger foe armed with a larger, more heavily enchanted blade. Both duelists are very heavily armored, but over time, Martin’s superior strength and magic can punch through the Halfling Hero’s defenses.

I still need to figure out:

  • What to do against touch-style attacks, like Wights and Vampires?  They become a lot deadlier under this system.
  • Do Hit Dice change? I’m thinking that combat between heavily armored dudes would take too long at standard Hit-Dice values.
  • Maybe each type of armor stays vulnerable to a particular type of damage (Piercing, Slashing, Bludgeon), if people think armor otherwise is too good.

Past Adventures of the Mule

June 2011

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