D20
Mutants & Masterminds uses a standard, or “core,” game mechanic to resolve actions. Whenever a character attempts an action with a chance of failure, do the following:
• Roll a twenty-sided die (d20)
• Add any relevant modifiers (for game traits like abilities, skills, powers, or circumstances) to the number rolled
• Compare the total to a number called a difficulty class (DC)
If the result equals or exceeds the difficulty class (set by the GM based on the circumstances), the effort succeeds. If the result is lower than the difficulty class, it fails. This simple mechanic is used for nearly everything in Mutants & Masterminds, with variations based on what modifiers are made to the roll, what determines the difficulty class, and the exact degree of success and failure.
Modifiers
Sometimes modifiers to the die roll are specified like this: “d20+2,” meaning “roll the twenty-sided die and add two to the number rolled.” An abbreviation of “d20–4” means, “roll the die and subtract four from the result.”
Percentages
You can also use the die to roll a percent chance of something in increments of 5% – just multiply the value of the die by 5 to get a percentage from 5% (a 1) to 100% (a 20). So if there’s a 45% chance of something, that’s a roll of 9 or less on the die.
DC | Skill Used |
Very easy (0) | Notice something in plain sight (Perception) |
Easy (5) | Climb a knotted rope (Athletics) |
Average (10) | Hear an approaching security guard (Perception) |
Tough (15) | Disarm an explosive (Technology) |
Challenging (20) | Swim against a strong current (Athletics) |
Formidable (25) | Climb a wet, slippery rock-face (Athletics) |
Heroic (30) | Overcome a sophisticated security system (Technology) |
Super-heroic (35) | Convinces the guards, even though you’re not wearing an ID badge and aren’t on their list, they should let you into the building (Deception) |
Nigh-impossible (40) | Track a trained commando through the jungle on a moonless night after 12 days of rainfall (Perception) |
Checks
Whenever a character in a game attempts something where the outcome is in doubt, it requires a check of an appropriate trait: ability, skill, power, etc. (also known as a “trait check” or a “[fill-in trait name]” check, like a “Dexterity check,” for example). Make a check by rolling the die, adding the appropriate rank, and comparing the result against a difficulty class (DC): if your result equals or exceeds the DC, you succeed. If it does not, then your attempt fails. Sometimes how much you exceed or fail to exceed the DC matters, but often it is simply whether you do or not that counts.
Check = D20 + Ability + Modifiers vs. Difficulty Class
Critical Success
If you roll a 20 on the die when making a check you’ve scored a critical success. Determine the degree of success normally and then increase it by one degree. This can turn a low-level success into something more significant, but more importantly, it can turn a failure into a full-fledged success! A critical success with an attack check is called a critical hit.
Routine Checks
A check normally represents performing a task under a certain amount of pressure, in the midst of the furious action of super-heroic adventure. When the situation is less demanding, you can achieve more reliable results.
Task | Check Using |
Sock a villain in the jaw | Close Combat skill (or Fighting) |
Climb the outside of a building | Athletics skill (or Strength) |
Do a triple-back flip | Acrobatics skill (or Agility) |
Find clues at a crime scene | Investigation skill (or Intellect) |
Notice a ninja sneaking up on you | Perception skill (or Awareness) |
Recall a particular fact | Expertise skill (or Intellect) |
Fix a broken device | Technology skill |
Convince someone of something | Deception or Persuasion skill (or Presence) |
Under routine circumstances—when you are not under any pressure—instead of rolling the die for the check, calculate your result as if you had rolled a 10. This ensures success for average (DC 10) tasks with a modifier of +0 or more. More capable characters (with higher bonuses) can succeed on more difficult checks on a routine basis: a +10 bonus, for example, means a routine check total of 20, able to succeed at DC 20 tasks on a routine basis, and achieve three degrees of success on average (DC 10) tasks on a routine basis.
The GM decides when circumstances are suitable for performing a task as a routine check. Certain game traits also change what tasks or situations are considered “routine” for a character. Routine checks help speed-up game play and smooth-out some of the variability of die rolling in situations where a character would be expected to perform at a steady, reliable level.
If a character’s routine check result is not up to a task, the player still has the option to roll the die, since the task is by definition not routine for that character. The idea behind routine checks is to eliminate die-rolling (and possible failures) for things competent characters should be able to accomplish on a regular basis, while still having a good idea of the characters’ capabilities.
Opposed Checks
Opposed checks offer the Gamemaster a useful tool for comparing the efforts of two characters quickly and easily. This applies not only to skills, but also powers and, in some cases, abilities. If two or more characters compete at a particular task, you can resolve it with an opposed check. The character with the highest check result wins. Of course, you can play things out if you want, but sometimes it’s good to be able to resolve things with a quick opposed check and move on.
As Gamemaster, if you find yourself without a particular rule to resolve a conflict or contest between characters, the opposed check is your friend. Pick the appropriate skill, power, or ability, make checks for the characters and compare the results to see how they did.
Some checks are opposed. They are made against another character’s check result as the DC. Whoever gets the higher result wins. An example is trying to bluff someone. You roll a Deception check, while the GM rolls an Insight check for your target. If you beat the target’s Insight check result, you succeed.
For ties on opposed checks, the character with the higher bonus wins. If the bonuses are the same, roll d20. On a 1–10, one character wins, and on an 11–20, victory goes to the other character; decide which character is “high” and which is “low” before rolling.
Task | Skill | Opposed By |
Sneak up on someone | Stealth | Perception |
Con someone | Deception | Insight |
Win a car race | Vehicles | Vehicles |
Pretend to be someone else | Deception | Perception |
Steal a key chain unnoticed | Sleight of Hand | Perception |
Win a trivia contest | Expertise | Expertise |
Break computer security | Technology | Technology |
Routine Opposition
In cases where two or more characters are actively opposing each other, both roll checks and compare the results. In some situations, however, one or more of the characters in an opposed check may not even be aware of it! For example, a guard standing watch and looking for intruders would make a Perception check to oppose any attempt at Stealth, but somebody just sitting in a park, not expecting anyone to sneak up on her, isn’t specifically looking. This is a case of routine opposition, in which case the DC for the active character’s check is the opposing character’s modifier +10, just like the result of a routine check (previously).
Active defenses in combat, where characters are focusing on other actions, are generally routine opposition, which is why attack checks are made against a DC of 10 + the appropriate defense. Active opposed checks in combat are an option when a character goes on the defensive.
Comparison Checks
In cases where a check is a simple test of one character’s capability against another, with no luck involved, both participants compare their appropriate ranks. The character with the higher rank wins. Just as you wouldn’t roll a “height check” to see who’s taller, you don’t need to make a Strength check to see who’s stronger; Strength rank already tells you that.
So when two characters arm wrestle, for example, the stronger character wins. If two flying characters race, the faster character wins, and so forth. Note this does not include the use of extra effort (see Extra Effort) to temporarily increase a character’s rank, which can affect the outcome of a comparison check, nor does it include things like maneuvers, tricks, or other ways of trying to affect the outcome. It assumes a straight-out comparison.
In the case of identical bonuses or ranks, each character has an equal chance of winning. Roll a die: on a 1–10, the first character wins, and on an 11–20, the second character does.
Graded Checks
Much of the time a check is a simple pass-fail, it either succeeds, or it does not. In other cases, it matters just how well the check succeeded, or how badly it failed. This gradation of results is called a graded check and involves a degree of success or failure.
Just rolling a success or failure counts as one degree. Every five full points a check result is over or under the difficulty class adds a degree. Fractions are ignored when determining degrees. So DC 10 check with a result of 13 is one degree of success, just as a result of 8 is one degree of failure.
There is no limit to the number of degrees a check may have, although more than two degrees of failure rarely matters, and some degrees of success may have no further effect beyond a certain point (once you have succeeded as well as is possible in a given situation). For example, failure on an Acrobatics check to balance means you wobble and spend that turn maintaining your balance, but don’t move. Two degrees of failure mean you lose your balance and fall! After that point, further degrees of failure don’t really matter.
In cases where a single degree of success or failure is sufficient, the rules simply specify “success” or “failure” without giving a degree. Specific types of graded checks—notably skill and resistance checks—give specific results for degrees of success and failure in their descriptions.
Check Result | Degree | Equal or Greater Than (DC 20) |
DC+15 | Four (Success) | 35 |
DC+10 | Three (Success) | 30 |
DC+5 | Two (Success) | 25 |
DC | One (Success) | 20 |
DC–5 | One (Failure) | 15 |
DC–10 | Two (Failure) | 10 |
DC–15 | Three (Failure) | 5 |
DC–20 | Four (Failure) | 0 |
Circumstances and Difficulty
Technically, circumstance modifiers could apply to either the check result of the difficulty class of a check, affecting the character’s performance, or making the task itself easier or harder. If you want to differentiate between circumstance modifiers that affect performance versus those that modify the difficulty of a task, feel free to do so. This game applies circumstance modifiers directly to the check result because it is easier to deal with them consistently, and the game effect is the same: the chance of success changes.
Some circumstances make checks easier or harder, resulting in a bonus or penalty to the check. Characters in a favorable situation are said to have a circumstance bonus for the check, while those in a disadvantageous situation are said to be have a circumstance penalty.
As a general rule, apply a modifier of plus or minus 2 if the character is at a minor bonus or minor penalty, and a modifier of plus or minus 5 if the character is at a major bonus or major penalty for the check:
+/-2 for bonus/penalty
+/-5 for major bonus/penalty
Attack Checks
An attack check determines whether or not you hit an opponent in combat with an attack. It is a d20 roll plus your bonus with that particular attack, usually based off of Fighting or Dexterity and appropriate modifiers, like the Close and Ranged Combat skills. The difficulty is your target’s defense class: Parry for close attacks, Dodge for ranged attacks. Certain attacks may target other defenses. If you equal or exceed your target’s defense class result, your attack hits. Otherwise, you miss.
Attack Check = D20 + Attack Bonus + Modifiers vs. Defense Class
A natural 20 on an attack check (where the die comes up 20) always hits and may be a critical hit (see Critical Hits in Action & Adventure for further information). A natural 1 on an attack check (where the die comes up 1) always misses, regardless of the check total. This differs from normal checks and reflects the variable and unpredictable nature of combat.
Resistance Checks
A resistance check is an attempt to resist different effects, ranging from damage and injury to traps, poisons, and various power effects. A Resistance check is a d20 roll + the appropriate defense (typically Dodge, Fortitude, Toughness, or Will).
Resistance Check = d20 + Defense Bonus + Modifiers vs. Hazard DC (generally 10 + rank)
The difficulty class is based on the strength of the hazard, such as the rank of an effect or the strength of a disease or poison, typically that value plus 10 (like a routine check). Resistance checks may be graded, with different results at different degrees.