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General Rules

Game Dice

The game is played with polyhedral dice. The conventional way to refer to a die is by the notation, not the actual geometric shape. The letter \(d\) followed by the number of faces: \(d2,\) \(d4,\) \(d6,\) \(d8,\) \(d10,\) \(d12,\) \(d20,\) and \(d100.\)

The usual notation used for rolling is \(NdF+M\), where \(N\) is the number of dice, \(F\) is the number of faces, and \(M\) is the roll's modifier. For a roll that looks like \(3d6+5\), this would mean roll 3 six-sided dice and add 5 to the resulting roll.

Percentile Dice

The \(d100\) is referred to as a percentile dice. These work a little differently, where rather than roll for the number, the number is generated. Two different \(d10\) are rolled. One gives the tens place and the other gives the ones.

The \(d20\)

The "default" die for the game is the \(d20\). It decides the success and failure of many actions. The resulting roll is generally modified by a character's ability score modifiers.

The success and failure is generally decided by a difficulty class (DC) or armor class (AC). Sometimes the DC or AC are explicit, but often times the GM decides. The goal is to meet or exceed the DC or AC.

Advantage and Disadvantage

Sometimes an roll gets a special modification called advantage and disadvantage. Advantage mean rolling two dice (or rolling twice) and taking the higher roll. Disadvantage is the opposite situation, roll two and take the lower roll.

If multiple situations affect a roll and each one grants advantage or imposes disadvantage on it, you don't roll more than one additional d20. If two favorable situations grant advantage, for example, you still roll only one additional d20.

If circumstances cause a roll to have both advantage and disadvantage, you are considered to have neither of them, and you roll one d20. This is true even if multiple circumstances impose disadvantage and only one grants advantage or vice versa. In such a situation, you have neither advantage nor disadvantage.

Ability Scores

Each of a creature's abilities has a score, a number that defines the magnitude of that ability. An ability score is not just a measure of innate capabilities, but also encompasses a creature's training and competence in activities related to that ability.

A score of 10 or 11 is the normal human average, but adventurers and many monsters are a cut above average in most abilities. A score of 18 is the highest that a person usually reaches. Adventurers can have scores as high as 20, and monsters and divine beings can have scores as high as 30.

Each ability also has a modifier, derived from the score and ranging from -5 (for an ability score of 1) to +10 (for a score of 30). Here is the formula for calculating ability score modifiers: $$ M = \frac{AS}{2}-5 $$ Where \(AS\) is the ability score.

Rounding

When dividing a number in game, round the result down if not whole.

Ability Checks

An ability check tests a character's or monster's innate talent and training in an effort to overcome a challenge. The DM calls for an ability check when a character or monster attempts an action (other than an attack) that has a chance of failure. When the outcome is uncertain, the dice determine the results.

To make an ability check, roll a d20 and add the relevant ability modifier. As with other d20 rolls, apply bonuses and penalties, and compare the total to the DC. If the total equals or exceeds the DC, the ability check is a success--the creature overcomes the challenge at hand. Otherwise, it's a failure, which means the character or monster makes no progress toward the objective or makes progress combined with a setback determined by the DM.

Skills

Each ability covers a broad range of capabilities, including skills that a character or a monster can be proficient in. A skill represents a specific aspect of an ability score, and an individual's proficiency in a skill demonstrates a focus on that aspect.

  • Strength-- measures natural athleticism and power output of the body
    • Athletics
  • Dexterity-- measures the physical agility, reflexes, balance, and poise of a character
    • Acrobatics
    • Sleight of Hand
    • Stealth
  • Constitution-- measures health, stamina, and vital force
  • Intelligence-- measures mental acuity, information recall, analytical skills
    • Arcana
    • History
    • Investigation
    • Nature
    • Religion
  • Wisdom-- measures awareness, intuition, and insight
    • Animal Handling
    • Insight
    • Medicine
    • Perception
    • Survival
  • Charisma-- measures confidence and eloquence
    • Deception
    • Intimidation
    • Performance
    • Persuasion

Sometimes, the DM might ask for an ability check using a specific skill--for example, “Make a Perception (Wisdom) check.” At other times, a player might ask the DM if proficiency in a particular skill applies to a check. In either case, proficiency in a skill means an individual can add his or her proficiency bonus to ability checks that involve that skill. Without proficiency in the skill, the individual makes a normal ability check.

Variant: Skills with Different Abilities

Normally, your proficiency in a skill applies only to a specific kind of ability check. Proficiency in Athletics, for example, usually applies to Strength checks. In some situations, though, your proficiency might reasonably apply to a different kind of check. In such cases, the DM might ask for a check using an unusual combination of ability and skill, or you might ask your DM if you can apply a proficiency to a different check. For example, if you have to swim from an offshore island to the mainland, your DM might call for a Constitution check to see if you have the stamina to make it that far. In this case, your DM might allow you to apply your proficiency in Athletics and ask for a Athletics (Constitution) check. So if you're proficient in Athletics, you apply your proficiency bonus to the Constitution check just as you would normally do for a Athletics (Strength) check. Similarly, when your orc barbarian uses a display of raw strength to intimidate an enemy, your DM might ask for a Intimidation (Strength) check, even though Intimidation is normally associated with Charisma.

Specific vs. General

Specific rules overrule general rules.