Basic Rules

The play of the Dungeons & Dragons game unfolds according to this basic pattern:

The DM Describes the Environment

The Dungeon Master (DM) tells the players where their adventurers are and what’s around them, presenting the basic scope of options available (such as how many doors lead out of a room, what’s on a table, who’s in the tavern, etc.).

The Players Describe Their Actions

Players then describe what they want to do. Sometimes one player speaks for the whole party, saying something like, “We’ll take the east door.” Other times, different adventurers might engage in separate actions: one might search a treasure chest while another examines an esoteric symbol 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 straightforward. If an adventurer wants to walk across a room and open a door, the DM might simply say that the door opens and describe what lies beyond. However, the door could be locked, the floor might conceal a deadly trap, or some other circumstance might complicate the task. In those cases, the DM determines what happens, often relying on the roll of a die to decide the outcome of an action.

The DM Narrates the Results

After the players take action, the DM narrates the results. This description often leads to another decision point, bringing the flow of the game right back to step 1. This pattern holds whether the adventurers are cautiously exploring a ruin, conversing with a devious prince, or engaged in mortal combat against a mighty dragon. In certain situations, particularly during combat, the action is more structured, and players (and the DM) take turns choosing and resolving actions. However, most of the time, play is fluid and flexible, adapting to the circumstances of the adventure. Much of the adventure takes place in the imagination of the players and the DM, relying on the DM’s verbal descriptions to set the scene. Some DMs like to use music, art, or recorded sound effects to enhance the mood, and many players and DMs adopt different voices for the various adventurers, monsters, and characters they portray. Occasionally, a DM might lay out a map and use tokens or miniature figures to represent each creature involved in a scene, helping players keep track of their positions.

The game uses polyhedral dice with different numbers of sides, which can be found in game stores and many bookstores. 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 used in many games). Percentile dice, or d100, work 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) provides the tens digit, while the other provides the ones digit. For example, rolling a 7 and a 1 results in a total of 71. Two 0s represent 100. Some ten-sided dice are numbered in tens (00, 10, 20, etc.), making it easier to distinguish between the tens and ones digits. In this case, a roll of 70 and 1 gives 71, while 00 and 0 gives 100.

When you need to roll dice, the rules specify how many dice of a certain type to roll and what modifiers to add. For example, “3d8 + 5” means you roll three eight-sided dice, add the results together, and then add 5 to the total. The same notation applies to expressions like “1d3” and “1d2.” To simulate a roll of 1d3, roll a d6 and divide the number rolled by 2 (rounding up). To simulate a roll of 1d2, roll any die and assign a 1 or 2 to the result depending on whether it was odd or even. Alternatively, if the number rolled exceeds half the number of sides on the die, it counts as a 2.

Does an adventurer’s sword swing hurt a dragon, or does it 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 do they 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, or d20, to determine success or failure.

Every character and monster in the game has capabilities defined by six ability scores: Strength (STR), Dexterity (DEX), Constitution (CON), Intelligence (INT), Wisdom (WIS), and Charisma (CHA). These scores typically range from 3 to 18 for most adventurers, although monsters might have scores as low as 1 or as high as 30. These ability scores, along with the ability modifiers derived from them, form 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 types of d20 rolls, forming the core of the game’s rules. All three follow these simple steps:

1. 1.

   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.

2. 2.

   Apply circumstantial bonuses and penalties. A class feature, a spell, a particular circumstance, or some other effect might provide a bonus or penalty to the check.

3. 3.

   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 usually determines target numbers and informs 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), while the target number for an attack roll is called an Armor Class (AC). This simple rule governs the resolution of most tasks in D&D play. 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.

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 making 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 would use the 5. If you have advantage and roll those numbers, you would use the 17.

There are three types of dice rolls we have talked about using a d20 in this chapter; Ability Checks, Attack rolls, and Saving throws. This section will explain what all of those are, how they work, and what to add to them. Ability Checks, Attack Rolls, and Saving Throws all fall under the umbrella term: D20 test.