The play of the Dungeons & Dragons game unfolds according to this basic pattern.
- The DM describes the environment. The DM tells the players where their adventurers are and what’s around them, presenting the basic scope of options that present themselves (how many doors lead out of a room, what’s on a table, who’s in the tavern, and so on).
- The players describe what they want to do. Sometimes one player speaks for the whole party, saying, “We’ll take the east door,” for example. Other times, different adventurers do different things: one adventurer might search a treasure chest while a second examines an esoteric symbol engraved on a wall and a third keeps watch for monsters. The players don’t need to take turns, but the DM listens to every player and decides how to resolve those actions.
Sometimes, resolving a task is easy. If an adventurer wants to walk across a room and open a door, the DM might just say that the door opens and describe what lies beyond. But the door might be locked, the floor might hide a deadly trap, or some other circumstance might make it challenging for an adventurer to complete a task. In those cases, the DM decides what happens, often relying on the roll of a die to determine the results of an action.
- The DM narrates the results of the adventurers’ actions. Describing the results often leads to another decision point, which brings the flow of the game right back to step 1.
This pattern holds whether the adventurers are cautiously exploring a ruin, talking to a devious prince, or locked in mortal combat against a mighty dragon. In certain situations, particularly combat, the action is more structured and the players (and DM) do take turns choosing and resolving actions. But most of the time, play is fluid and flexible, adapting to the circumstances of the adventure.
Often the action of an adventure takes place in the imagination of the players and DM, relying on the DM’s verbal descriptions to set the scene. Some DMs like to use music, art, or recorded sound effects to help set the mood, and many players and DMs alike adopt different voices for the various adventurers, monsters, and other characters they play in the game. Sometimes, a DM might lay out a map and use tokens or miniature figures to represent each creature involved in a scene to help the players keep track of where everyone is.
The game uses polyhedral dice with different numbers of sides. You can find dice like these in game stores and in many bookstores.
In these rules, the different dice are referred to by the letter d followed by the number of sides: d4, d6, d8, d10, d12, and d20. For instance, a d6 is a six-sided die (the typical cube that many games use).
Percentile dice, or d100, work a little differently. You generate a number between 1 and 100 by rolling two different ten-sided dice numbered from 0 to 9. One die (designated before you roll) gives the tens digit, and the other gives the ones digit. If you roll a 7 and a 1, for example, the number rolled is 71. Two 0s represent 100. Some ten-sided dice are numbered in tens (00, 10, 20, and so on), making it easier to distinguish the tens digit from the ones digit. In this case, a roll of 70 and 1 is 71, and 00 and 0 is 100.
When you need to roll dice, the rules tell you how many dice to roll of a certain type, as well as what modifiers to add. For example, “3d8 + 5” means you roll three eight-sided dice, add them together, and add 5 to the total.
The same d notation appears in the expressions “1d3” and “1d2.” To simulate the roll of 1d3, roll a d6 and divide the number rolled by 2 (round up). To simulate the roll of 1d2, roll any die and assign a 1 or 2 to the roll depending on whether it was odd or even. (Alternatively, if the number rolled is more than half the number of sides on the die, it’s a 2.):3 :6
Does an adventurer’s sword swing hurt a dragon or just bounce off its iron-hard scales? Will the ogre believe an outrageous bluff? Can a character swim across a raging river? Can a character avoid the main blast of a fireball, or does he or she take full damage from the blaze? In cases where the outcome of an action is uncertain, the Dungeons & Dragons game relies on rolls of a 20-sided die, a d20, to determine success or failure.
Every character and monster in the game has capabilities defined by six ability scores. The abilities are Strength, Dexterity, Constitution, Intelligence, Wisdom, and Charisma, and they typically range from 3 to 18 for most adventurers. (Monsters might have scores as low as 1 or as high as 30.) These ability scores, and the ability modifiers derived from them, are the basis for almost every d20 roll that a player makes on a character’s or monster’s behalf.
Ability checks, attack rolls, and saving throws are the three main kinds of d20 rolls, forming the core of the rules of the game. All three follow these simple steps.
- Roll the die and add a modifier. Roll a d20 and add the relevant modifier. This is typically the modifier derived from one of the six ability scores, and it sometimes includes a proficiency bonus to reflect a character’s particular skill. (See chapter 1 for details on each ability and how to determine an ability’s modifier.)
- Apply circumstantial bonuses and penalties. A class feature, a spell, a particular circumstance, or some other effect might give a bonus or penalty to the check.
- Compare the total to a target number. If the total equals or exceeds the target number, the ability check, attack roll, or saving throw is a success. Otherwise, it’s a failure. The DM is usually the one who determines target numbers and tells players whether their ability checks, attack rolls, and saving throws succeed or fail.
The target number for an ability check or a saving throw is called a Difficulty Class (DC). The target number for an attack roll is called an Armor Class (AC).
Advantage and Disadvantage
Sometimes an ability check, attack roll, or saving throw is modified by special situations called advantage and disadvantage. Advantage reflects the positive circumstances surrounding a d20 roll, while disadvantage reflects the opposite. When you have either advantage or disadvantage, you roll a second d20 when you make the roll. Use the higher of the two rolls if you have advantage, and use the lower roll if you have disadvantage. For example, if you have disadvantage and roll a 17 and a 5, you use the 5. If you instead have advantage and roll those numbers, you use the 17.
Specific Beats General
This book contains rules, especially in parts 2 and 3, that govern how the game plays. That said, many racial traits, class features, spells, magic items, monster abilities, and other game elements break the general rules in some way, creating an exception to how the rest of the game works. Remember this: If a specific rule contradicts a general rule, the specific rule wins.
Exceptions to the rules are often minor. For instance, many adventurers don’t have proficiency with longbows, but every wood elf does because of a racial trait. That trait creates a minor exception in the game. Other examples of rule-breaking are more conspicuous. For instance, an adventurer can’t normally pass through walls, but some spells make that possible. Magic accounts for most of the major exceptions to the rules.:4 :7
There’s one more general rule you need to know at the outset. Whenever you divide a number in the game, round down if you end up with a fraction, even if the fraction is one-half or greater.:4 :7