I must create a system, or be enslaved by another man's. I will not reason and compare: my business is to create.

- William Blake

Saturday, February 17, 2024

Hitting armor in D&D + glancing blows

Here's another idea on weapon versus armor. 

Assume ascending AC: 10 if unarmored, 12 for leather, etc.

If you roll less than 10 (or a natural 1), you miss. But if you roll a number higher than 9 an lower than AC, you hit armor.

This part is intuitive. Maybe you already use something similar when narrating combat: "17? You hit him, but your sword is deflected by his armor", etc.

Now give each type of weapon an Armor Piercing (AP) rating. Maybe a maximum of 50% (heavy mace) and a minimum of 10% (natural weapons). Unarmed attacks get AP 0.

When you hit armor, you deal a fraction of your full damage  round down.

And that's it! 

A +1 bonus due to magic or dexterity bonuses can save you on a roll of 11, for example (no damage).

Easy right?

Most (not all) side effects are positive for me:

* When a giant hits you - even in plate armor - you'll get hurt. Dexterity might be more useful here...
* Everything becomes more dangerous, so many give a few additional HP. 
* Armor is a bit less useful so this requires some balancing (make it lighter or raise all ACs).

The downside is adding more crunch.

We could go one step further and do the same with speed... From 10% to 90% chance of getting an extra attack, roll once for all combatants. Or roll to see if you can interrupt a spell before it is cast, etc.

But that is another matter...

Glancing blows

Here is an easier/lighter alternative.

An exact hit (e.g., rolling 17 against AC 17) is a "glancing blow", dealing a fraction of damage (or -x damage, depending on the weapon). 

Against very high AC, glancing blows will happen very often (e.g., once for every four hits), but against low AC there will be little difference in damage per round.

The effect is similar: some weapons are better against armor. However, the impact of this rule is much smaller.

(What is more, maybe a glancing blow gives you a chance of getting a free attack - so that quick weapons are more useful against unarmored targets!)

This might just be easy enough to actually try to implement in my B/X games...


  1. I don't get the second approach: The exact number has always a 5% chance to happen, regardless of AC.

    But I like the first idea. Its not too much crunch either. You can rule it happens only for certain weapons (maces, big concussive hits) so its not something happening all the time

    1. Second approach: think in terms of DPR. if you only hit 20% of the time (e.g., plate + shield), 5% is one out of four hits. But against unarmored foes, it barely matters.

      In any case, the difference might be too small to matter anyway.

      I prefer the first approach too! The only caveat is that makes combat a bit more deadly and armor a bit less useful, so probably requires more fine tuning. Applying it only to a few weapons is a great idea; so these weapons would really shine against armor.

    2. now I get the second approach and its brilliant too. Very nice idea man. I think it would work even better on a less granular roll (2d6 or 1d12 for example) as the exact number would happen more (on 1d12) or on different rates depending on armor (2d6).

    3. Thanks! I agree, using a d12 or 2d6 would definitely add more impact to the rule!