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Hawke's d20 Hit Location and Critical Hit Severity System

by admin published Jun 02, 2015 01:35 AM, last modified Aug 17, 2015 07:50 PM
Posted by Hawke at Sep 26, 2014 07:55 PM - Filed under: DnD, 5th Edition, Dungeons & Dragons, Original Dungeons & Dragons, D&D Next, rpg, OD&D, D&D - How many times have you rolled that d20, added the bonuses, and had an awesome total (though not a “Nat 20”), and thought “What a waste of a great roll” because then you just roll your normal damage dice. Wouldn't it be nice if the greater the d20 hit roll, there would be a gradient of increasingly more severe consequences to the target being hit?

Though I run d20 games regularly, I miss the days of Role-master and MERP with the detailed critical systems. However, they required extra rolls, and were arbitrary in hit location.

I have always wanted to have hit location and critical details for d20, and I think I finally found the solution...

I have tried many different approaches to trying to add hit location and detailed critical results to the d20 system, and up until now, have not been satisfied with the results.

I have used the old Armory d30 (yes, thirty-sided) system. I have used the old Original D&D rules from the Blackmoor Supplement with percentile for hit location. And some of my players that later have become DM's have integrated that as well, having their players roll a d20 with percentile simultaneously. But it still lacked details for critical hits (other than just plain multiplying of damage).

I do not care for hit points just being totally abstract and not reflecting specific wounds, only overall health (as 5th edition really emphasizes abstraction of HP, and takes it to an extreme that I totally disagree with, allowing them to completely restore all hit points from a single long rest!), and prefer something with some detail.

For decades I have just arbitrarily had players (and myself) add details to the attacks when they hit, describing a slash across the chest, or crunching sound to the arm, etc.

I also looked at Monte Cooke's d20 3.x publication best of d20, but that too didn't quite work as desired.

A Little History

During the 1980s I pretty much bought every single AD&D 1st edition product ever made, then they started the whole process over again with 2nd edition, and I stopped buying TSR products until moving to Spokane in 2004.

Meanwhile I played many other RPGs; MERP, Rolemaster, Twilight 2000, Call of Cthulhu, Star Wars, Star Trek, and scores of others, and not a single TSR/Wizards product during the interim. So I never actually played much of 2nd edition (other than the first players hand book, DMG, and MM when they first came out), and missed all the other supplements.

In recent years, as I have been working on my RPG Research project ( ), I have been picking up used copies of 2nd Edition AD&D for very little money $2 to $9 per item typically.

AD&D 2nd Edition

I recently started looking through them and stumbled across the combat screen, that included the rules from the supplement "Players Options: Combat Tactics". And within was a critical hit location system. I read the relevant section of the book, and realized that here was something that possibly could work with all versions of d20, but it needed some improvements from the original.

The original just sets a wider critical range, but with more requirements to qualify, and then if qualifies as a critical hit, then making an additional roll to see which location is hit (1d10) between arms, legs, abdomen, chest, and head, and then again to determine the severity of the hit (determined by earlier rolls). It kind of works, but after play testing it with a few groups, it significantly slowed down combat situations, and not only made encounters take longer, it also slowed down the action so that players became less interested, rather than more. Once again that balance between detail and speed....

Crits With No Extra Rolls Needed

So, I thought about trying to make the system work without adding ANY rolls. I have been through other variants with only one roll (hit location for example) and that is okay, but the current beta versions I am testing requires ZERO additional rolls from the standard d20 to hit, and then damage dice.

I am looking for more play testers to poke holes at any problems with it, and welcome constructive feedback on ways to improve this system.

There are likely to still be some problems with this version of the rules, but the beginnings of testing with this version looks promising with 1st Edition AD&D, 3rd edition, and 5th edition (I haven't ever found anyone willing to play 4th edition).

Though explaining this approach takes a lot of verbiage in written form, it actually is quite quick and simple when actually implemented.

Gradient Severity

How many times have you rolled that d20, added the bonuses, and had an awesome total (though not a “Nat 20”), and thought “What a waste of a great roll” because then you just roll your normal damage dice. Wouldn't it be nice if the greater the d20 hit roll, there would be a gradient of increasingly more severe consequences to the target being hit? Of course, this works both ways, the PCs are at greater risk as well, which for my style of play/GM emphasizing R-O-L-E-playing over R-O-L-L-playing (aka hack 'n' slash, min-maxing, munchkin play, IMnsvHO) encourages players to find non-combat solutions since the risk of combat is more deadly to all parties involved.

How It Works

The basic premise is that there is a quick math calculation used multiple times, instead of multiple rolls. Here is the basic version (still needs work):

An attacker rolls a standard d20, applies any to hit bonuses, for the total to hit roll. If the total is less than is normally requires to hit, nothing is different. If the total is exactly the amount needed to hit, the attacker just rolls hit points (it is 0 above the necessary to hit roll). If the attack total is 1 or more above the necessary amount, then it registers on the hit location chart. For those of you that do not have the 2nd Edition screen with the crits, I am including them here, but modified for my tastes (borrowing from RM/MERP and such).

The type of weapon determines which of three weapon charts are consulted; Piercing, Bludgeoning, Slashing. All three use the same hit location, but have different detailed descriptions for specific wounds based on the critical type.

These rules are expressed in terms that can work with any version of d20, whether OD&D, AD&D 1st, AD&D 2nd, D&D 3.x, D&D 4, or D&D 5th edition. With OD&D through 2nd Edition, it is based on charts and THACO, while D&D 3.x+ is based on the DC number for AC, either way, the key is simply knowing what the normal number needed to roll to hit is, and then just calculating the difference.

Formulaic Version

Target Number (TN) needed to hit. D20 Actual Roll (AR) before modifiers. Total Hit Roll (THR) (d20 roll + modifiers). Difference to Hit (DR)

THR-TN=DR if DR=0, just roll normal HP damage if DR=1-3, just calculate hit location and normal HP damage, but do not calculate Severity Results. If DR=4+, calculate hit location, Severity Results (SR), and total HP damage (in this order).

Hit Location (HL) = AR-10, reference Chart #1 for Hit Location. Hit Severity (HS) = THR-TN=DR, reference appropriate critical hits chart (bludgeon, piercing, slashing), appropriate to the already calculated Hit Location.

Don't worry about the abbreviations, it is just for expressing the formula.

Explained Version

What all this really means is that there are ZERO additional rolls for this system, just some quick and simple math calculations and simple chart consultation.

The first step is to determine if the hit was successful, if it exceeeded the minimum to hit, and by how much.

If the total modified roll result is equal to the hit roll needed, then the hit only causes just normal damage (difference between to-hit number, and to-hit roll is 0).

If the difference is 1-3 above the necessary total to hit, then determine hit location and HP damage, but no need to calculate severity.

If the difference is 4+ above necessary total to hit, then determine hit location, hit severity, and HP damage.

Hit Location – Chart #1

So, if needing to determine hit location (if 1+ above needed to hit), it is calculated by subtracting 10 from the actual rolled d20 amount (without modifiers): 0-1 Arm (shield/off) 2-3 Arm (weapon) 4-5 Leg (shield/off/leading leg) 6-7 Leg (weapon/rear leg) 8 Abdomen (or lower back) 9 Torso (or upper back) 10 Head

This approach will ALWAYS yield a result between 0 to 10 (or a negative inverse). If they rolled 9 or lower (and somehow still hit due to bonuses, prone, etc.), just use the negative number in the inverse, so if result is -3, would be.

Example 1

Need 15 to hit, roll 13, with a +2 combination of modifiers to hit for a total of 15. Difference is 15-15=0. Do not determine hit location or severity, just roll normal HP damage.

Example 2

Need 15 to hit. Rolled 13 with a +4 combination of modifiers to hit for a total of 17. The difference is 17-15=2. This qualifies for hit location determination, though severity calculation is not necessary. Hit location = 13-10=3, which would be the target's weapon arm. Then roll normal HP damage, though narrating that it hit their arm (or arm armor), the target may grunt in pain, and maybe have a minor cut, abrasion, or bruise, but without any bleeding or breaking of bones or tendons, etc.

Example 3

Need 20 to hit. Rolled 19, with +9 total modifiers, for a total of 28. This is 8 above needed hit number, so definitely qualifies for both hit location and effects calculation. Hit location Is 19-10=9, which is Torso (or upper back). Hit Severity Effects Cross reference effects for appropriate weapon type (bludgeon, piercing, or slashing), under the Torso chart. The total difference to determine severity is 8 above needed to hit, so it would be result 8 on the chart (we'll use piercing in this instance): Torso injured, Major Bleeding, ½ move, -4 penalty to all actions.

Example 4

Need 23 to hit. Rolled 18, with a total of +19 in total modifiers (higher level), for total of 37. This is 14 above needed hit number, so definitely qualifies for both hit location and effects calculation. Hit location Rolled 18 so 18-10=8, which is abdomen. Hit Severity Effects In this case using a bludgeoning weapon, cross reference for the Abdomen, the total difference between the total needed to hit, and actual total calculated roll is 14, so consult the 13+ Effects result: “Abdomen destroyed, victim killed”.

Optional Rule for Fatal Hit Severity Effects

If not comfortable with being able to kill a target in a single (exceptional) blow, can optionally just use the next less-severe result, but keep the triple damage result to differentiate from a weaker hit.

Optional Rule for Called Shots

Called shots = penalty to hit is equal to the higher hit location number? For example if calling shot on shield arm, a -1, if weapon arm -3, if off leg -5, if weapon leg -7, if abdomen -8, if torso -9, if head -10. This can be interpreted as a minus to the attackers roll, or as a bonus to the target's total armor class. If the attacker calls the shot, AND beats the modified total, then they get the critical result for that targeted location calculated as normal but at the desired location. If they do NOT beat that total, then the COMPLETELY MISS. If this gets too easy to hit the critical parts (abdomen, torso, or head), the consider simply adding 4 to the modifier, or doubling the modifier.

Again, I have only had about 1 session of play testing with three different groups, using three different versions of D&D so far, so I'm sure there are flaws I haven't thought of that will come our through use. If interested in helping me play test this, please let me know, and I will create and upload a PDF with the full charts to let people try poking holes in the system and see if there are any additional fixes needed.

I hope you find it useful and enjoyable. Happy Gaming! -Hawke Robinson


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