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Hawke's d20 Crit System for Any Version d20 / D&D

by admin last modified Jun 01, 2015 11:39 PM
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Hawke's d20 Crit System for Any Version d20 / D&D

Posted by admin at June 01. 2015

Hawke's no additional rolls d20 hit location and critical hit rules for all versions of d20 / Dungeons & Dragons

ted by Hawkeat October 05. 2014

Hawke's No Additional Rolls Critical System for d20 (All Versions) Based on AD&D; 2nd Edition, but modified to not add any additional Rolls Beta Version 20140926a

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 wanted to have hit location and critical details for d20. 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 adapted 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 overall health (as 5th edition really emphasizes, and takes 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 was very lacking.

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.

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 here was something that possibly could work with all versions of d20, but it needs some improvements from the original.

The original just sets a wider crit range, but with more requirements, and then if a critical hit, then rolling 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.... 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.

This still has some problems that I am trying to work out, but the basic version is working well both with 1st Edition AD&D; and with 3rd edition and 5th edition (I haven't ever found anyone willing to play 4th edition). 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 invovled.

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.

Change hit location as follows to make more sense in combat and without rolling hit location: From most likely to be hit (and least likely to be fatal), to least likely/most critical (head).

Try different direction in calculation. Use Total -10 for hit location, and use total modified to hit roll difference as severity determination, that makes more sense yes?

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.

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

Re: Hawke's d20 Crit System for Any Version d20 / D&D

Posted by admin at June 01. 2015

Posted by Hawkeat October 05. 2014

Version 20141005c - Updated. Now includes Leg and Arm hit location and results severity tables. More on the way. Attached as PDF.
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