Making a skill check for a creature follows these steps.
- Roll a d20.
- Add the creature's skill check modifier for the skill.
- Add any situational modifiers that apply, including any bonuses or penalties from powers affecting the creature.
- Figure out the total, which is called the check result.
- Compare the check result to the Difficulty Class (see below) to see if the check succeeds.
The elements of the check account for the creature's training, natural talent (ability modifier), overall experience (one-half the creature's level), other applicable factors (relevant bonuses), and sheer luck (a die roll).
Difficulty Class
When making skill checks, high results are best. A creature is always trying to meet or beat a certain number, referred to as the Difficulty Class (DC) of the check. A skill check's DC depends on what a creature is trying to accomplish with the skill check, and the number is set by the Dungeon Master.
Typically, a creature either succeeds or fails at a skill check, meaning that the check result meets or exceeds (beats) the DC or else falls below it. Some skill checks have degrees of success or failure that depend on the difference between the check result and the DC. Unless otherwise noted, when a creature fails a skill check, it can try again with a new check.
The skill entries in this section give sample DCs for common uses of the skills. Some DCs are fixed, whereas others scale with level. A fixed DC represents a task that gets easier as an adventurer gains levels. By the time an adventurer reaches the epic tier, certain tasks become trivial. In contrast, a DC that scales with level represents a task that remains at least a little challenging throughout an adventurer's career.
The Dungeon Master can use the suggested DC for a task or set one using the Difficulty Class by Level table. The table provides DCs at each level for three categories of difficulty: easy, moderate, and hard. When choosing a DC from the table, the Dungeon Master should use the level of the creature performing the check, unless otherwise noted.
The following definitions help the Dungeon Master determine which of the three DCs is appropriate for a particular check. The goal is to pick a DC that is an appropriate challenge for a particular scenario or encounter.
- Easy: An easy DC is a reasonable challenge for creatures that do not have training in a particular skill. Such creatures have about a 65% chance of meeting an easy DC of their level. An easy DC is a minimal challenge for a creature that has training in the skill, and is almost a guaranteed success for one that also has a high bonus with the skill. In group checks or when every adventurer in a party is expected to attempt a given skill check, particularly when no one necessarily has training, an easy DC is the standard choice for the scenario.
- Moderate: A moderate DC is a reasonable challenge for creatures that have training in a particular skill as well as for creatures that don't have training but do have a high score (18 or higher) in the skill's key ability. Such creatures have about a 65% chance of meeting a moderate DC of their level. In a skill challenge, a moderate DC is the standard choice for a skill check that a single creature is expected to make.
- Hard: A hard DC is a reasonable challenge for creatures that have training in a particular skill and also have a high score (18 or higher) in the skill's key ability. Such creatures have about a 65% chance of meeting a hard DC of their level. A hard DC is the standard choice for a skill check that only an expert is expected to succeed at consistently.
Opposed Checks
Sometimes a creature makes a skill check that tests its ability against that of another creature using either the same skill or a different one. A creature's Stealth modifier, for instance, measures that creature's ability to hide against another creature's ability to spot it using the Perception skill. These skill contests are called opposed checks.
In an opposed check, two creatures make checks, and the higher result wins. If there's a tie, the creature with the higher skill check modifier wins. If it's still a tie, both sides roll again.
Checks Without Rolls
In some situations, luck does not affect whether a skill check succeeds or fails. Two special types of checks reflect this fact: taking 10 and passive checks.
Taking 10
When creatures are not in a rush or not involved in an encounter or a skill challenge, they can choose to take 10 on a skill check. When a creature takes 10, its player doesn't roll a d20 for the skill check. Instead, the check result is determined as if the player had rolled a 10, meaning the result equals 10 + the creature's skill check modifier. For mundane tasks, taking 10 usually results in a success.
Passive Checks
When creatures aren't actively using a skill, they're assumed to be taking 10 for any opposed checks using that skill. Doing so is called making a passive check. Passive checks are a convenient way to use creatures' skills without bogging the game down with die rolls.
For example, a group of adventurers is walking through an area without making Perception checks to look for danger, so each character is assumed to be using his or her passive Perception to notice hidden objects and creatures. If an adventurer's passive Perception beats a creature's Stealth check, the adventurer notices the creature without having to make a Perception check. If the adventurer's passive Perception and the creature's Stealth check are the same, the adventurer notices the creature if his or her Perception modifier is higher than the creature's Stealth modifier.
Passive checks are most commonly used for Perception checks and Insight checks, but the DM might also use a passive check for a skill such as Arcana or Dungeoneering to determine how much the characters know about a monster at the start of an encounter.
Aid Another
In some situations, creatures can work together to use a skill or an ability. A creature can help another make a skill check or an ability check by taking the aid another action. Given a choice, a group of adventurers should have the character who has the highest ability modifier or skill check modifier take the lead, while the other characters cooperate to provide assistance.
| Aid Another: |
| Action: Standard action. When a creature takes this action, it chooses a target adjacent to it. DC: The assisting creature makes a skill check or an ability check against a DC equal to 10 + one-half its level. Success: The target gains a +2 bonus to the next check using the same skill or ability before the end of the assisting creature's next turn. Failure: The target takes a -1 penalty to the next check using the same skill or ability before the end of the assisting creature's next turn. This penalty represents the distraction or interference caused by the failed assistance. |
A creature can affect a particular check only once using the aid another action. However, up to four creatures can use aid another to affect a single check.
In certain circumstances, the DM might decide that only fewer than four creatures—or even no creatures—can try to aid a check. For instance, it is unlikely that more than one creature can assist in picking a lock.
Group Checks
The Dungeon Master sometimes asks the adventurers to make a check as a group. Doing this is called making a group check, which is useful when a number of individuals are trying to accomplish something as a group. In such a situation, the characters who are skilled at a particular task help cover those who aren't.
To make a group check, everyone in the group makes a skill check or an ability check specified by the DM. A group check is almost always against an easy DC. If at least half the group succeeds, the whole group succeeds. Otherwise, the group fails.
Group checks might come up in a variety of situations: when the adventurers try to sneak past some sentries (using Stealth), try to scale a sheer cliff together (using Athletics), use disguises to pass as a group of orc soldiers (using Bluff), and so on. Such checks are particularly common in skill challenges.