A recap of the original Dungeons & Dragons rules by Gary Gygax and Dave Arneson, revised in B/X editions by Tom Moldvay, David “Zeb” Cook, and Steve Marsh, and further updated by Gavin Norman in Old-School Essentials rules.
ROLES
* Fighter: Experienced with all weapons for battle.
* Cleric: An intermediary between mortals and spirits.
* Magic-User: A master of arcane spell formulae.
* Thief: An expert in stealth and infiltration.
* Dwarf: A stout and resilient warrior.
* Elf: An adept in both spells and swords.
* Halfling: A small and stealthy warrior.
House Rule: Clerics who use edged weapons loose the turning undead ability but keep all other class powers (saving throws, spellcasting).
Character creation: See Fast Character B/X Creator.
ABILITIES
* Strength (STR): Physical prowess, melee weapons.
* Dexterity (DEX): Agility, reflexes, ranged weapons.
* Constitution (CON): Health, fortitude, concentration.
* Intelligence (INT): Knowledge, memory, reason.
* Wisdom (WIS): Awareness, empathy, willpower.
* Charisma (CHA): Appeal, communication, leadership.
ABILITY SCORE MODIFIERS
* -4 … Ability Score 1 (Minimal)
* -3 … Ability Score 2 to 3 (Semi)
* -2 … Ability Score 4 to 5 (Inferior)
* -1 … Ability Score 6 to 8 (Low)
* +0 … Ability Score 9 to 12 (Fair)
* +1 … Ability Score 13 to 15 (High)
* +2 … Ability Score 16 to 17 (Exceptional)
* +3 … Ability Score 18 to 19 (Genius)
* +4 … Ability Score 20 to 21 (Supra-Genius)
* +5 … Ability Score 22 to 23 (Superior)
CRITICAL RESULTS (house rule for use beyond combat)
* Any d20 roll of a 20 is an automatic success.
* Any d20 roll of a 1 is an automatic failure.
ABILITY CHECKS
Roll d20 + one related ability modifier. Totals equal to or higher than a difficulty target number succeed.
* Target Number 7 … Easy tasks
* Target Number 14 … Hard tasks
* Target Number 21 … Extreme tasks
Opposed Checks: Side with the highest total wins. Re-roll tied totals.
Group Checks (House Rule): Each member rolls. Use highest result, +1 per other helper who succeeded and -1 per helper who failed.
Progress Checks (House Rule): Each check per round/minute/hour adds to a target total (10 for simple tasks, 20 for complex tasks) for when a task is completed.
Non-Failures (House Rule): A failed dice roll check may still succeed at the expense of some cost: time, equipment, or suffering damage.
SKILL CHECKS
Two methods…
* #-IN-6 METHOD: Roll the listed number of less for success (e.g. “1-in-6 chance of spotting a secret door”).
* d100 PERCENTILE METHOD: Roll equal to or less than a percentage chance of success (e.g. “91% chance to climb sheer surfaces”).
SAVING THROW
* Roll d20 + (with DM’s approval) one related ability modifier. Totals equal to or higher than a difficulty target number avoid or reduce harm from a threat.
* Target numbers are set by a character’s role and other modifiers.
ATTACK ROLLS (Characters)
* Roll d20 + modifiers equal to or higher a target number set by the character’s role and target’s Armor Class rating.
* Add an attacker’s Strength modifier for attacks using melee weapons, or Dexterity modifier to missile/ranged attacks.
* On a successful hit, roll for damage based on the weapon type. Add Strength modifier to melee attacks.
* In old rules, lower AC is better protection. Since 2000, higher AC (Ascending Armor Class, or AAC) is better.
Armor Class
* AC 9/AAC 10 … Unarmored
* AC 7/AAC 12 … Light armor (leather)
* AC 5/AAC 14 … Medium armor (chainmail)
* AC 3/AAC 16 … Heavy armor (plate mail)
* AC 1/AAC 18 … Extreme armor (dragon scales)
* AC -1/AAC +1 … Shield
* AC -1/AAC +1 … Dexterity score 13 to 15
* AC -2/AAC +2 … Dexterity score 16 to 17
* AC -3/AAC +3 … Dexterity score 18 to 19
ATTACK ROLLS (Non-Player Characters, Monsters)
* Roll d20 + NPC’s Hit Dice + modifier equal to or higher a target number set by the character’s role and target’s Armor Class rating.
* On a successful hit, roll for damage based on the attack type.
HIT POINTS
* Represents a mix of size, toughness, determination, and luck.
* At 0 hit points, a creature dies but (house rule: …but may be revived if healed before next turn).
* Natural healing restores 1d3 hit points per day of rest.
TIME AND MOVEMENT
* Combat: 40 feet per round (10 sec.)
* Running: 120 feet per round (10 sec.)
* Exploring (Indoors/Underground): 120 feet per turn (10 min.)
* Exploring (Outdoors): 360 feet per turn (10 min.)
Note: While exploring, characters must rest every 6th turn (50 minutes exploring, 10 minutes resting). If not rested, characters suffer -1 on all d20 rolls.
Movement and Encumbrance (Humans)
* 120′ (40′) … Unarmored and carrying less than 40 lbs. (400 coins)
* 90′ (30′) … Light armor or carrying 41 to 60 lbs. (600 coins)
* 60′ (20′) … Medium armor or carrying 61 to 80 lbs. (800 coins)
* 30′ (10′) … Heavy armor or carrying 81 to 160 lbs. (1,600 coins)
Movement and Encumbrance (Animals)
* 120′ (40′) … Mule carrying up to 200 lbs. (2,000 coins)
* 60′ (20′) … Mule carrying 201 to 400 lbs. (4,000 coins)
VISION AND LIGHT
* Torch: Illuminated 30-foot radius, lasts for 1 hour (6 turns).
* Lantern: Illuminates 30-foot radius, lasts for 4 hours (24 turns) on one flask of oil.
* Light spell: Illuminated 30-foot radius, lasts at least 1 hour (6 turns) plus longer for higher caster levels.
* Continual Light spell: Illuminates 60-foot radius, never goes out.
* Infravision: See heat, cannot be used to read in the dark, spoiled by normal or magical light.
COMBAT ENCOUNTERS
Per Turn of Exploration
* 1. In a dungeon, the DM checks for wandering monsters every other turn (1-in-6 chance every 20 minutes). In wilderness, check 1 to 3 times daily. At sea, once daily.
* 2. Characters enter area, listen, search. Detecting traps or secret doors in each 10’x10’x10′ area takes one person 1 turn (10 minutes) to check.
* 3. If no monsters are encountered, turn ends.
* 4. On 6th turn each hour, party must rest for 1 turn (10 minutes) to avoid a -1 penalty on future d20 rolls.
* 5. Check party resources: Depleting light sources, encumbrance changes, spell durations.
* 6. Party may change marching order for next turn.
Monster Encounters
* 1. Roll 2d6 for distance between sides. If area is smaller, shorten the distance accordingly.
Distance
* 2: 20 feet
* 4: 40 feet
* 6: 60 feet
* 7: 70 feet
* 9: 90 feet
* 12: 120 feet
* 2. Each side rolls 1d6 for surprise. A roll of 1 or 2 means surprise, unable to move or act in first round.
* 3. If monsters surprised and party not surprises, party may slip away unnoticed or hide before being noticed.
* 4. Roll 2d6 for monster reaction…
Reactions
* 2: Immediate attack.
* 3 to 5: Hostile, possible attack.
* 6 to 8: Uncertain, confused.
* 9 to 11: No attack, monster leaves or considers offers.
* 12: Enthusiastic friendship.
* 5. Each side reacts: Talk, flee, pursue, or fight.
* 6. If fight, each side rolls 1d6 for initiative. Higher result acts first, re-roll ties. Repeat initiative check each round.
* 7. Individuals on each side may act in any order each combat sequence step.
* 8. Once the fight is over, the turn ends.
Combat Sequence Per Round
* 1. Morale: Check opponent morale. (2d6 equal or below Morale number; check after side’s first casualty or if half the side is incapacitated)
* 2. Movement: Move characters and creatures (typically up to 40 feet).
* 3. Missile attacks: Resolve ranged attacks and damage. (Short range +1 “to-hit,” long range -1 penalty.)
* 4. Spellcasting: Cast spells and resolve their effects. (Multiple spells may be maintained at once.)
* 5. Melee attacks: Resolve hand-to-hand attacks and damage. (Side chooses order of attacks.)
* Other side repeats sequence next.
* Re-roll initiative after both sides have gone through this sequence.
Combat Modifiers
* +Strength modifier: Melee or unarmed attack.
* +Dexterity modifier: Missile/ranged attack.
* +1: Missile/ranged attack at short range.
* +0: Missile/ranged attack at medium range.
* -1: Missile/ranged attack at long range.
* -1 to -4: Target partially behind cover (20%, 40%, 60%, 80%).
* Cannot hit: Target completely behind cover.
* +2: Opponent retreating, exhausted, or attacked from behind.
* +4: Thief attacking with backstab.
* +1 to +3: Attacking with magic weapon.
* +1: Halfling using a missile weapon.
* +1: Attacker subject of Bless spell.
* +1: Attacker subject of Blight spell.
* -1: Attacking target protected by Protection from Evil spell (when applicable).
* -4: Attacking without looking directly at an opponent (such as a medusa).
* +2: Opponent attacking someone who deliberately avoids looking at them.
* -2: Attacker nauseated or confused by a monster’s special ability.
* -2/-4: Making two attacks with two weapons, -2 on primary and -4 on secondary.
* Automatic hit: Attacking a paralyzed or helpless target.
DAMAGE PER HIT
* 1: Unarmed Strike
* 1d4: Club, dagger, sling stone, torch.
* 1d6: Arrow, crossbow bolt, hand axe, mace, short sword, spear, war hammer.
* 1d8: Battle axe (two-handed), sword; also, flask or burning oil.
* 1d10: Greatsword (two-handed), Pole arm (two-handed).
DAMAGE MODIFIERS
* +Strength modifier (melee)
* +1 to +3: Damage from magic weapon.
COMBAT HOUSE RULES
* Sweep Attacks: When fighting creatures with 1 HD or less, a Fighter may make one attack per Level each combat round.
* Automatic Cleave: When an attacker reduces an enemy to 0 hit points with a melee attack, the attacker may immediately make another melee attack against another enemy within reach.
* Reckless Attack: Each round, an attacker may gain a +2 “to-hit” on one melee attack but suffer -2 AC until acting again in the next round. If the reckless attack hits, add the Fighter’s Level to the damage. (No bonus damage for non-fighters.)
* Rapid Shots: Each round, an attacker may fire two missile attacks at one or two targets at a -3 “to-hit” penalty for each attack.
* Evasion: A character who foregoes an attack or other action and focuses on avoiding attacks gains +2 AC until next round’s actions.
* Shield Sacrifice: A character may choose to let one attack destroy an equipped shield and avoid all damage from that hit.
* Time to Die: At 0 or less hit points, a creature may be revived if healed to 1 hit point before its next turn, else it dies.
* Intimidate: As an action instead of attacking, a character may force one enemy with HD no greater than the character’s Level to make a morale check.
* Energy Drain: Each hit permanently reduces a creature’s maximum hit points by an amount equal to the Hit Dice of the attacker. The character’s Level is unaffected. A creature reduced to 0 hit points this way instantly dies.
CHASES HOUSE RULE
* Roll 2d6 for a distance value between evader and pursuer.
* For each step of the chase (per round indoors, per turn if in wilderness), each side rolls d20.
* If one side is a step faster, such as 120′(40′) chasing 90′(30′), the faster side gets a +3 bonus and slower a -3 penalty. If two steps faster, 120′(40′) versus 60′(20′), the modifiers are +6 and -6.
* The side with the higher result changes the distance count by 1, either up or down.
* When the distance count reaches 0, the pursuer has caught up to the evader.
* When the distance count reaches 13, the evader has fully escaped the pursuer.
* During each step, either side may attempt actions to hinder the other: Spells, missile fire, and so forth.
EQUIPMENT
Containers
* 20 lbs. (200 coins) … Small sack
* 60 lbs. (600 coins) … Large sack
* 40 lbs. (400 coins) … Backpack
SPECIAL SITUATIONS (includes house rules)
* Falling: Suffer 1d6 damage per 10 feet fallen.
* Starvation: A full day without food or water imposes a cumulative -1 penalty on all d20 rolls. For each day without food, take 1d2 damage and lower maximum hit points by the same amount. For each day without water, take 1d8 damage and lower h.p.
* Suffocation:: Survives a number of rounds equal to a creature’s Constitution score.