Dungeons & Dragons gameplay

Since the 3rd edition Dungeons & Dragons role-playing game, game mechanics and die rolls determine much of what happens. These include:


 * Ability scores, the most basic statistics of a character, which influence all other statistics
 * Psionic ability, a superhuman ability stat that rarely, if ever, occurs by chance in some gifted characters
 * Extraordinary senses, what innately superior perceptions a (typically non-human) character might possess
 * Armor class, how well-protected a character is against physical attack
 * Hit points, how much punishment a character can take before going unconscious or dying
 * Saving throws, a character's defenses against nonphysical or area attacks (like poisons, fireballs, and enchantments)
 * Attack rolls and attacks, how effectively a character can score hits against, and inflict damage to, another character
 * Skills, how competent a character is in various areas of expertise
 * Feats, what special advantages a character has through natural aptitude or training

Ability scores
All player characters have six basic statistics:
 * Strength (STR): Strength is a measure of muscle, endurance and stamina combined. Strength affects the ability of characters to lift and carry weights, melee attack rolls, damage rolls (for both melee and ranged weapons,) the Jump, Climb, and Swim skills, several combat actions, and general checks involving moving or breaking stubborn objects.
 * Dexterity (DEX): Dexterity encompasses a number of physical attributes including hand-eye coordination, agility, reflexes, fine motor skills, balance and speed of movement; a high dexterity score indicates superiority in all these attributes. Dexterity affects characters with regard to initiative in combat, ranged attack rolls, Armor Class, Reflex saves, and the Balance, Escape Artist, Hide, Move Silently, Open Lock, Ride, Sleight of Hand, Tumble, and Use Rope skills. It also affects the number of additional attacks of opportunity granted by the Combat Reflexes feat.  Dexterity is the ability most influenced by outside influences (such as armor).
 * Constitution (CON): Constitution is a term which encompasses the character's physique, toughness, health and resistance to disease and poison. The higher a character's Constitution, the more hit points that character will have. Constitution also is important for Fortitude saves, the Concentration skill, and fatigue-based general checks.  Constitution also determines the duration of a barbarian's rage. Unlike the other ability scores, which render the character unconscious or immobile when they hit 0, having 0 Constitution is fatal.
 * Intelligence (INT): Intelligence is similar to IQ, but also includes mnemonic ability, reasoning and learning ability outside those measured by the written word. Intelligence dictates the number of languages a character can learn, and it influences the number of spells a preparation-based arcane spellcaster (like a Wizard) may cast per day, and the effectiveness of said spells. It also affects how many skill points a character gains per level, the Appraise, Craft, Decipher Script, Disable Device, Forgery, Knowledge, Search, and Spellcraft skills, and bardic knowledge checks.
 * Wisdom (WIS): Wisdom is a composite term for the character's enlightenment, judgment, wile, willpower and intuitiveness. Wisdom influences the number of spells a divine spellcaster (like clerics, druids, paladins, and rangers) can cast per day, and the effectiveness of said spells.  It also affects Will saving throws, the Heal, Listen, Profession, Sense Motive, Spot, and Survival skills, the effectiveness of the Stunning Fist feat, and a monk's quivering palm attack.
 * Charisma (CHA): Charisma is the measure of the character's combined physical attractiveness, persuasiveness, and personal magnetism. A generally non-beautiful character can have a very high charisma due to strong measures of the other two aspects of charisma. Charisma influences how many spells spontaneous arcane spellcasters (like sorcerers and bards) can cast per day, and the effectiveness of said spells.  It also affects Bluff, Diplomacy, Disguise, Gather Information, Handle Animal, Intimidate, Perform, and Use Magic Device checks, how often and how effectively clerics and paladins can turn undead, the wild empathy of druids and rangers, and a paladin's lay on hands ability.

An ability score is a natural number, with a value of 10 or 11 representing average human ability.

Additional:
 * Comeliness (COM): In the original version of AD&D Comeliness was introduced as a 7th Ability Score/Stat in the supplemental rulebook Unearthed Arcana and Oriental Adventures to differentiate between physical attractiveness and Charisma. Comeliness has not appeared as an officially supported ability score since, although the second edition rules Player's Option: Skills & Powers introduced a subability score named "Appearance."

3.0 and 3.5 editions
Each score has a modifier (mod), where Modifier = (Score − 10)/2, rounded down. So, for example, an ability score of eight would result in a modifier of −1 ((8−10)/2 = −1), while an ability score of 17 gives you a modifier of +3 ((17−10)/2 = 3.5). This modifier is added to the appropriate dice rolls. For example, the strength mod would be added to the damage dealt by a sword, the dexterity mod to Armor Class (see below) as the character's ability to dodge attacks, and the charisma mod to an attempt to smooth-talk a merchant.

There are creatures that lack certain ability scores (undead, for example, have no constitution). These are called nonabilities and affect how that creature is treated by certain spells and effects. The aforementioned undead, for example, are immune to almost anything that requires a Fortitude save, unless it can also affect objects. This is not the same as having a score of zero (which causes death, paralysis or unconsciousness depending on the ability in question).

Determining ability scores
There are several methods of determining a character’s initial ability scores during character creation:


 * Rolling dice (3d6): This is the standard method for some pre-3.0 editions. For each ability score, the player rolls 3d6, and adds the values, resulting in scores ranging from three to eighteen, averaging between 10 and 11.
 * Rolling dice (4d6k3): This is the standard method for 3.0 and 3.5 editions. For each ability score, the player rolls 4d6, and adds the three highest values, resulting in scores ranging from three to eighteen, skewed towards higher numbers, averaging 12.2446, though the most probable result is 13.
 * Predetermined array of scores: Less random, but inflexible.
 * Point buy: In the point buy system, a player has a certain number of points to spend on their ability scores. The more powerful the characters are intended to be, the more points will be available to the players. (Characters are usually more powerful for a more difficult game.) Possible ability scores range from eight to eighteen, and each score has a certain point cost affixed to it, where higher scores tend to cost more points per level than lower ones. This method is used in Dungeons & Dragons Online (and other computerized D&D-based games, such as Neverwinter Nights) to avoid imbalanced characters getting an unfair advantage over other players.

Extraordinary senses

 * Blindsight and blindsense: These abilities represent acute nonvisual senses, such as echolocation, electroreception, or an acute sense of hearing or smell. Blindsight, introduced in the 3rd edition Monster Manual, allows a creature to discern the shape of its surroundings and locate and identify creatures, negating all visibility-related combat penalties. In the 3.5 edition, blindsight is generally only possessed by creatures which lack a visual sense, such as oozes, although there are some exceptions, such as whales. Blindsense, a variant of blindsight introduced in the 3.5 edition Monster Manual, is more limited: it allows a creature to discern the rough locations of other creatures, but does not negate the other effects of concealment or poor visibility. When a creature possesses blindsight or blindsense, the specific senses represented by the ability are generally specified. No races from the Player's Handbook possess blindsight or blindsense.
 * Darkvision: This refers to the ability of a creature to see in the dark. It allows the creature to discern shapes (as in normal, daylight vision) but only in shades of grey. Darkvision was introduced in the 3.0 edition of the game to replace both Ultravision and Infravision, which had become seen by some designers of the game as too logically inconsistent to continue using as-is.
 * Infravision: One of the predecessors of Darkvision, in all the early editions (Original, Basic, and Advanced, in all editions thereof) of the game, which was loosely based on the premise of the infrared spectrum. It allowed some races to see in darkness by discerning the heat signatures left behind by other creatures. However, under the game rules description it was described as seeing in total darkness just as one would outdoors on a clear night under a bright full moon. This attribute was present in many demi-human races that lived above ground - such as the Elves (non Drow).
 * Low-light vision: Introduced in the 3rd edition Player's Handbook, low-light vision allows a character to see better in poor lighting conditions.
 * Tremorsense: Introduced in the 3rd edition Monster Manual, creatures with tremorsense have an acute ability to sense vibrations, allowing them to locate other creatures in contact with the ground or in the water. No PHB races possess tremorsense.
 * Ultravision: Another predecessor of Darkvision, in the Advanced editions of the game, loosely based on the premise of the ultraviolet spectrum, was essentially identical to Darkvision in all but name. This attribute was usually only reserved for those races that lived exclusively in the dark or underground, such as the Drow (Dark Elves).

Armor class
Armor Class (AC) is a rating used to determine how difficult it is to damage a creature/character. It is based on several factors such as a creature's natural aversion to physical injury, magical enhancements, and any protective garments worn. The base stat of Dexterity grants bonuses to AC.
 * In the original game, Armor Class ranged from 9 to 0, because armor and dexterity modifiers were applied to hit rolls instead. Negative values first appeared in the Greyhawk supplement, because it first applied them directly to the Armor Class.
 * In some editions of the game prior to 3.0, Armor Class ranges from -10 to 10. Having an AC of 10 was the weakest, and a -10 being the strongest possible written AC.
 * In 3.0, 3.5, and 4th editions, Armor Class instead starts at 10 and increases. Extremely non-dextrous or non-moving creatures may suffer penalties that lower their Armor Class below 10.

Defenses
Starting with 4th edition, there are three Defenses that function similarly to Armor Class. Fortitude is based on Strength or Constitution; it represents a character's endurance to pain. Reflex is based on Dexterity or Intelligence and can be modified by a shield; it represents a character's ability to dodge. Will is based on Wisdom or Charisma; it represents a character's strength of mind and resistance to mental attack. These defenses are typically lower than AC, so an attack against Fortitude is usually better than an attack against AC.

Hit points
Hit points (HP) are a measure of a character's vitality or health; they are determined by the character's class (certain occupations breed hardier people) or race, and Constitution score. Hit points are reduced whenever a character takes damage.

In the original D&D game, as well as first edition AD&D, a character died when his/her hit point total reached 0. In second edition, an optional rule was introduced in which a character died when his/her hit points reached -10, with beings falling unconscious at 0 HP, and living creatures reduced to negative HPs continue to lose additional HPs due to bleeding, etc. unless they are stabilized by chance or healing (natural or magical); in third edition, this rule became part of the core rules.

In fourth Edition, death occurs when a character's Hit Point value is reduced to the character's Bloodied value expressed as a negative number. For example, if a character has Hit Points of 52 (and therefore a Bloodied value of 26), this character is unconscious and dying at 0 hit points and death occurs when his/her hit points reach -26.

Saving throws
Certain situations give characters the chance to avoid special types of danger or attacks. These chances are called saving throws or saves. A saving throw is made when a character would come to harm from extraordinary means such as poisons and magical compulsions in nature.

Pre-d20 system
In the pre-d20 System editions of D&D, there are five categories of saving throws:
 * '''Paralysis, Poison, or Death Magic
 * Petrification or Polymorph
 * Rods, Staves, Wands (magical devices)
 * Spells
 * Breath Weapons (such as with dragons or gorgons)

3rd edition
There are three kinds of Saving Throws:
 * Fortitude: A Fortitude save represents physical toughness, incorporating stamina, ruggedness, physique, bulk, metabolism, resistance, immunity, and other similar physical qualities. Fortitude saves involve a character's resistance to an effect that directly attacks his health, stamina, or soul. This includes resisting poison, shrugging off the worst of a flesh to stone spell, and ignoring the horrible stench that surrounds a ghast.  Typically, Fortitude saves are the sort of thing that a "tough guy" would be good at.  Fortitude saves are affected by the Constitution base stat.
 * Reflex: A Reflex save represents physical (and sometimes mental) agility, incorporating quickness, nimbleness, hand-eye coordination, overall coordination, speed, and reaction time. Reflex saves involve a character's ability to move out of the way of an incoming object or spell effect as well as his ability to leave an area in a short amount of time. This includes the character's ability to dodge falling rocks and his ability to escape the worst of a Fireball spell.  Typically, Reflex saves are the sort of thing that an agile person would be good at.  Reflex saves are affected by the Dexterity base stat.
 * Will: A Will save represents inner strength, incorporating willpower, mental stability, the power of the mind, levelheadedness, determination, self-confidence, the superego, and resistance to temptation. Will saves involve a character's mental resistance to mental dominance, confusion, stress, and insanity. This includes the character's ability to resist a charm person spell, see through an illusion, and to resist supernatural fear.  Typically, Will saves are the sort of thing that a confident or determined person would be good at.  Will saves are affected by the Wisdom base stat.

4th edition
In 4th edition there is only one type of saving throw. The Difficulty Class (DC) for every saving throw is 10, although a few abilities and powers give you bonuses to your saving throws. Saving throws are usually rolled after you have already been affected by an attack (by hitting your AC or your Fortitude, Reflex, or Will defense, defenses which the 3rd edition saves had been converted into), rolled each round to give you a chance to shake off the effect. They are meant partly to simplify record-keeping for effects that last more than one round but less than the encounter.

Attacking
When a character makes an attack a 20-sided die is rolled to determine success/failure. The result could be adjusted based on any number of possible modifiers the character or its intended target have.

The number added to the die roll is actually several different modifiers combined, coming from different places. These modifiers include the character's proficiency with the specific weapon and weapons in general, the quality of the weapon (masterwork craftsmanship or magical enhancements), the modifier of the ability associated with the weapon (strength for melee, or close-quarters weapons, and dexterity for ranged weapons), magical effects improving/hampering the character's ability to attack, and any special experience the character has fighting a certain foe.


 * In the original and 1st edition of the game, and in the Basic game, the final result is compared to a table along with the target's Armor class to see if the attack hits. Every general class type had its own matrix-style table, while "monsters" or "creatures" per se used the same matrix as the generic fighter character type.
 * In the 2nd edition of the game, if the final result equals or exceeds the attacker's THAC0 (the pre-recorded number the character needs To Hit Armor Class 0"), the attacker has successfully hit a target with armor class 0. If the target has an armor class different from zero (which is far more likely than not), the target's Armor Class is subtracted from the attacker's THAC0, and that number is what the attacker's roll must equal or exceed to see if the attack hits.
 * In 3.0 and 3.5 editions, the attack hits simply if the final result is equal to or greater than the target's Armor Class.
 * In 4th edition, attack abilities can be based on any one of the ability scores, not just dexterity and strength, and usually determined by class, and can target any one of the defenses mentioned above. As with 3rd and 3.5 edition, the attack hits if the number rolled equals or exceeds the targeted defense.

Actions
The combat mechanic is turn-based and operates in rounds. A round is a discrete time interval (approximately 6 seconds, game-time in later editions, and approximately 1 minute in earlier editions) in which all involved parties act in the combat. The order in which parties involved in the combat act is determined by Initiative.


 * In pre-3.0 editions of the game, characters are allowed to move their speed and attack every round, or perform a reasonable combination of other actions.
 * In 3.0 and 3.5 editions, what a character can and cannot do in a given round is more codified; a character may perform one standard and one move action, two move actions or one full-round action in a round, along with any number of free actions, and a single swift or immediate action. Unlike other types of actions, immediate actions may also be taken during someone else's turn, though that counts as using the immediate action slot for the character's following turn.
 * In 4th edition, a character is allotted one standard action, one move action, one minor action, and any number of free actions to be performed during his or her turn. Each action can be downgraded, such as replacing a standard action with a move action or a move action with a minor action, with results similar to 3.5's possible combinations of actions. In addition, a character may take one opportunity action during each other character's turn, and one immediate action during any round, defined as the time between the end of the character's turn and the beginning of his next turn. Immediate and opportunity actions each have a defined trigger that allows their use, based on other characters' actions, and are categorized as reactions that are resolved after the trigger or as interrupts that are resolved before or in place of the triggering event. Neither immediate nor opportunity actions may be taken during the character's turn.

Skills
Dungeons and Dragons, starting with the 2nd Edition of the game and continuing to the current 4th Edition, has many skills that characters may train in. In the 2nd Edition these were broken down into Weapon and Non-Weapon Proficiencies. In the 3rd they are all simply referred to as "Skills", not to be confused with "Feats", below. Characters gain skill points for buying skill ranks based on class, level, and intelligence. Some skills can only be taken by certain classes, such as Read Lips or Animal Empathy. These skills are called exclusive skills. Others can be used even if the character has no ranks in that skill (i.e., is not trained in that skill).

A skill check is always a d20 roll, with bonuses from the number of skill ranks, the skill's key ability, and any miscellaneous modifiers (from spells or racial abilities, for instance). Sometimes, a skill check may be aided by favorable circumstances (such as you brandishing a weapon while using Intimidate) or hampered by unfavorable circumstances (such as using improvised tools to pick a lock).

An example of a skill is Search, which is Intelligence-based; an example of a miscellaneous modifier which could be applied to search is the +5 competence bonus for a character wearing the "Goggles of Minute Seeing". Other skills include Diplomacy (CHA), Escape Artist (DEX), Swim (STR), various Knowledge skills (like Knowledge (Arcana) or Knowledge (Local)) (INT), Spot (WIS), and Concentration (CON).

A "check" is successful when the roll is higher than or equal to the Difficulty Class (DC) of the task. Usually, the Dungeon Master sets the DC. Sometimes the DC is set by the result of something else's check, this is an "opposed check". An example of an opposed check is spot against hide: the character is trying to see something else that is hidden/trying not to be seen.

From 3.5 to 4th edition, the list of skills was drastically reduced. This usually resulted in each skill covering a broader range of activities, though some skills were removed entirely, such as Profession and Craft. The skill rank system was also removed, each skill being instead trained or untrained, with a constant bonus given to any trained skill along with a bonus based on the character's level. A character begins with a number of trained skills based on and chosen according to his class. The character gains new skill training only through spending a feat for that purpose, though these may be chosen regardless of class.

Feats
Feats were introduced in 3rd edition of Dungeons & Dragons. They are similar to the proficiencies of 2nd edition, giving characters more depth in a structured way for the game.

A feat is an advantage, often some special option for the character (such as a special combat maneuver) or some modification to game options and the mechanics involved. Feats can be contrasted with skills, which were also introduced in the same edition, in that using a feat does not usually require the particular success/fail roll that skills do. Instead of possessing a certain rank at a skill, a character either possesses a feat or does not.

There are many different types of feats. Some are magical; such as "Silent Spell" which allows a spellcaster to cast a spell without speaking words. Others are combat-related, such as "Weapon Focus" which gives a bonus to attack rolls when a character is using a certain weapon (such as a longsword). Another example is "Leadership", which allows the character to attract henchmen and followers.

Many feats, especially the most powerful ones, require certain prerequisites (such as related feats or minimum ability scores) in order to select that feat. Some feats provide continual effects, while others, typically ones that have some cost to use or can be used to a variable degree, must be declared before use.

Feat types: Ambush, Bardic, Ceremony, Combat Form, Divine, Domain, Epic, Exalted, General, Heritage, Item Creation, Luck, Metamagic, Metapsionic, Psionic, Reserve, Tactical, Vile, Wild

The 4th Edition feat system is similar to the system in 3.5, with each feat having any number of prerequisites and some beneficial effect. Feats are also categorized by type, though "general" feats lack a category. "Class" and "Racial" feats require the character to be the indicated class or race. The "Heroic", "Paragon", and "Epic" descriptors indicate that the character must be in that tier or higher in order to choose the feat. "Divinity" feats grant a character with the "Channel Divinity" power an additional, alternative use for that power.

Feat types: Class, Divinity, Multiclass, Racial, Heroic, Paragon, Epic