Ability score impact in B/X

 In the early days of Dungeons & Dragons, ability scores had little function in the game but to act as prime requisites for the three (eventually four) classes, determining whether a character received a bonus to earned experience points. When they did affect resolution of actions during actual game play, the impact was limited to a bonus or penalty of + or -1. As the game evolved, ability scores began to apply more directly to in-game actions, such as attack and damage rolls and saving throws, and the range of adjustments was expanded. With the increase in the role of ability scores, they became important to all classes, not just the one for whom each is a prime requisite, and their relative importance and impact also shifted greatly, with some becoming very powerful and others much less so. In this post, I'm going to analyze the power of each ability in the B/X D&D rules, including factors such as which rolls or stats an ability modifies, the relative magnitude of modifiers vs. the rolls or stats they modify, how often they are used in play, and the consequences of the actions modified.

Strength, of course, is highly useful in melee combat. In the real world, a combatant's strength affects both his offensive and defensive capabilities. A strong warrior can not only strike harder to cause greater injury, he's more effective at battering aside his opponent's blocks and parries, and is more able to block and parry attacks in turn. In D&D, Strength modifies attack rolls and damage rolls, a double-dip ability. The same modifier is used for both, so it has a modest impact on the d20 roll to attack, and an outsized effect on the much smaller dice (typically d4 to d10) used to roll damage. The table below shows the chance to hit, average damage per damage roll, and average damage per round at each level of Strength adjustment, assuming a 1st level character using a 1d6 weapon attacking a target with AC9.

	-3	-2	-1	0	+1	+2	+3
Attack vs. AC9	13 (40%)	12 (45%)	11 (50%)	10 (55%)	9 (60%)	8 (65%)	7 (70%)
Average Damage Roll	1.5	2.0	2.5	3.5	4.5	5.5	6.5
Average Damage/Round vs. AC9	0.6	0.9	1.25	1.925	2.7	3.575	4.55

As you can see, the damage per round from the Str 18 character is more than 7 times that of the Str 3 character, but even comparing less extreme jumps shows dramatic differences. A -1 to a +1 bonus more than doubles damage output, for example. And the tougher the target's AC, the greater the disparity, as can be seen in the table below.

	-3	-2	-1	0	+1	+2	+3
Attack vs. AC5	17 (20%)	16 (25%)	15 (30%)	14 (35%)	13 (40%)	12 (55%)	11 (60%)
Average Damage Roll	1.5	2.0	2.5	3.5	4.5	5.5	6.5
Average Damage/Round vs. AC5	0.3	0.5	0.75	1.225	1.8	3.025	3.9

A few points of Strength can make a very large difference in combat effectiveness, and attack and damage rolls are by far the most frequently made in the game, and taken all together, perhaps the most consequential to an individual character's and an adventuring party's success.

Intelligence, in the game, affects a character's literacy, or lack thereof, and the number of languages spoken, and that's it. (Leaving out its value as a prime requisite to the magic-user and elf classes specifically.) In real life, intelligence is a monumentally important ability, strongly influencing one's capacity for logic and reason, creative thinking, and learning and integrating new skills and knowledge. These things are also important in D&D, but primarily for the player rather than the character. Attempting to model the functions of Intelligence for the character steps heavily on the toes of player skill and agency. Granted, being able to read messages scrawled on a dungeon wall or clues recorded in musty old tomes, and speaking the tongues of a common monster species or two are often handy abilities, but for the most part, Intelligence as a character stat is pretty much neutered. As long as you don't have an extremely low score, it's not likely to be much of a hindrance, and a very high score is of limited help, and probably only for a limited span of your career too. (Speaking Orc may be useful for a beginning adventurer, but it's likely to be much less so when you've progressed to fighting giants and dragons.) Strictly by the book, Intelligence doesn't modify any dice rolls in the game.

Wisdom's sole canonical purpose in the game, aside from being the PR of the cleric class, is to adjust "magic-based" saving throws. Exactly what is meant by "magic-based" is not entirely clear; whether it applies to all spells and magic item effects, let alone such magical abilities as a basilisk's petrifying attacks or a mummy's disease-causing touch is up to DM interpretation. Saving throws are often the last, or only, chance to avoid death or other fate that would remove a character from play, so an individual saving throw may be one of the most consequential rolls in the game. Even taking the broadest possible interpretation of "magic-based" saving throws, though, they're vastly less frequent than attack and damage rolls, making Wisdom seldom of even potential value, and then only when the margin of success or failure of a save is no greater than the Wisdom adjustment. As saving throws are rolled on d20, that means the Wisdom modifier has a modest effect at best. As with Intelligence, many of the more important functions of Wisdom as it is defined in the rules belong to the player. Deciding whether a risk is worth taking or not, or intuitively grasping the significance of some dungeon feature or clue are hard to model without impinging on player skill and agency, making Wisdom of marginal use at best to anyone who isn't a cleric.

Dexterity in B/X D&D modifies a character's Armor Class and attack rolls with missile weapons (whether thrown or fired by a device such as a bow.) Unlike the compounding effects of Strength's double-dip adjustments to attack rolls and damage, Dexterity affects the outcomes of attacks in a linear fashion, and it applies only to d20 rolls where its effect is much less relative to Strength's modification of damage dice rolls. The adjustment to AC modifies average damage sustained from attacks by +/-5% of the base average damage per point of adjustment per round. Thus, against a foe with a d6 weapon, each point of Dex bonus reduces average damage per round by 0.175 points (3.5 average for d6 x 5%.) The bonus to missile attacks modifies average damage inflicted per round of firing missiles by +/-5% of the base damage per point of adjustment; thus by 0.175 damage points per point of Dex modifier for a d6 weapon. Dexterity clearly has an impact in the game, but less than Strength. A low Dex is less of a hindrance in combat than a low Str, and likewise a high Dex is of less benefit than high Str.

Constitution modifies hit points per Hit Die rolled. As such, it's the only ability score to scale with a character's level. It also exerts an oversized influence on each die, since hit points are rolled with d4, d6, or d8 according to class. The maximum adjustment of +/-3 is larger than the average roll of 2.5 on a d4, and still quite hefty even on a d8. I've already written about how Constitution's impact is so great that a low score can render some classes virtually unplayable. A high score can be extremely impactful in the other direction, potentially accounting for half or more of a character's total hp at 9th level. (An 18 Con provides 27 bonus hp at level 9. Hit points from Hit Dice only average 22.5, 31.5, and 40.5 for d4, d6, and d8 respectively.) 

Charisma modifies the rolls to determine monster and NPC reactions, and to the number of retainers a character may employ at a time. Depending on the DM, reaction rolls are likely to be very frequent, and they're rolled with 2d6, making the impact of a point of adjustment weigh heavier than it would on a d20 roll. Reactions can also be of great consequence during an adventure, making the difference between being able to walk away peacefully or risking hp and resources in a battle with little to gain, or even possibly gaining a helpful ally. A +1 Cha modifier boosts the chances of at least a non-hostile reaction (6 or higher) from 72.22% to 83.33%, and the chances of a friendly result (12) from 2.78% to 8.33%! Reducing combats by almost 10% is nothing to sneeze at. 

The Charisma-imposed limits on the number of retainers may or may not be important in a game. It's likely to be relatively inconsequential if there are many player-characters involved, but in a game with only one or two players, a Charisma score high enough to maintain a good stable of retainers just may be the most crucial ability for success!

Unlike Intelligence and Wisdom, Charisma in-game doesn't necessarily negate player skill and agency. The player still decides whether to parley at all, what to say, and the general tone; Charisma represents a more intangible factor. 

In conclusion, I would rate the relative power of each ability in the game as follows:

1. Constitution

2. Strength

3. Charisma

4. Dexterity

5-6 (tie) Intelligence and Wisdom