Source Player Core pg. 392
When success isn't certain—whether you're firing a laser pistol at a sentry robot, attempting to balance on a moving conveyor belt, or straining to remember the name of the ambassador's pet squox at a soiree—you attempt a check.
All types of checks, from skill checks to attack rolls to saving throws, follow these basic steps.
Roll a d20 and identify the modifiers, bonuses, and penalties that apply.
Calculate the result.
Compare to the DC.
Determine the degree of success and the effect.
Checks and Difficulty Classes (DCs) both come in many forms. When you fire your laser pistol at that sentry robot, you make an attack roll against its Armor Class, which is the DC to hit another creature. As you try to balance on that conveyor belt, you attempt an Acrobatics skill check with a DC based on the terrain you're traversing. When calling to mind the name of the ambassador's pet squox, you attempt a check to Recall Knowledge. You might use either the Society skill or a Lore skill you have that's relevant to the task, and the DC depends on how common the knowledge of the pet's name might be, or possibly how many drinks your character had when the ambassador showed them the pet's infosphere page the night before.
No matter the details, for any check you must roll the d20 and achieve a result equal to or greater than the DC to succeed.
When the likelihood something will happen or fail to happen is based purely on chance, you'll attempt a flat check. A flat check never includes any modifiers, bonuses, or penalties—you just roll a d20 and compare the result on the die to the DC. Only abilities that specifically apply to flat checks can change the checks' DCs; most such effects affect only certain types of flat checks.
If more than one flat check would ever cause or prevent the same thing, just roll once and use the highest DC. In the rare circumstance that a flat check has a DC of 1 or lower, skip rolling; you automatically succeed. Conversely, if one ever has a DC of 21 or higher, you automatically fail.
Start by rolling your d20. You'll then identify all the relevant modifiers, bonuses, and penalties that apply. A modifier can be either positive or negative, but a bonus is always positive, and a penalty is always negative. The sum of all the modifiers, bonuses, and penalties you apply to the d20 roll is called your total modifier for that statistic.
Fortune and misfortune effects can alter how you roll your dice. These abilities might allow you to reroll a failed roll, force you to reroll a successful roll, allow you to roll twice and use the higher result, or force you to roll twice and use the lower result.
You can never have more than one fortune effect or misfortune effect come into play on a single roll. For instance, if an effect lets you roll twice and use the higher roll, you can't then use Meyel's Chosen (a fortune effect) to reroll if you fail. If multiple fortune effects would apply, you have to pick which to use. If two misfortune effects apply, the GM decides which is worse and applies it.
If both a fortune effect and a misfortune effect would apply to the same roll, the two cancel each other out, and you roll normally.
Nearly all checks allow you to add an attribute modifier to the roll. Attribute modifiers represent your raw capability and are described in the sidebar here. Exactly which attribute modifier you use is determined by what you're trying to accomplish. Usually, firing a gun applies your Dexterity modifier, whereas remembering the name of the ambassador's pet uses your Intelligence modifier.
When attempting a check that involves something you have some training in, you also add your proficiency bonus. This bonus depends on your proficiency rank: untrained, trained, expert, master, or legendary. If you're untrained, your bonus is +0—you must rely on raw talent and any situational bonuses. Otherwise, the bonus equals your character's level plus a certain amount depending on your rank. If your proficiency rank is trained, this bonus is equal to your level + 2, and higher proficiency ranks further increase the amount you add to your level.
Proficiency Rank | Proficiency Bonus |
Untrained | 0 |
Trained | Your level + 2 |
Expert | Your level + 4 |
Master | Your level + 6 |
Legendary | Your level + 8 |
There are three other types of bonus that frequently appear: circumstance bonuses, item bonuses, and status bonuses. If you have different types of bonuses that would apply to the same roll, you'll add them all. But if you have multiple bonuses of the same type, you can use only the highest bonus on a given roll—they aren't cumulative. For instance, if you have both a proficiency bonus and an item bonus, you add both to your d20 result, but if you have two item bonuses, you add only the higher of the two.
Circumstance bonuses involve the situation you find yourself in when attempting a check. For instance, using Raise a Shield with a compact shield grants you a +1 circumstance bonus to AC. Being behind cover grants you a +2 circumstance bonus to AC.
Item bonuses are granted by some item that you are wearing or using, either mundane or magical. For example, armor gives you an item bonus to AC, while a tactical holoskin grants you an item bonus to Impersonate someone using the Deception skill while wearing it.
Status bonuses typically come from spells, other magical effects, or something applying a helpful, often temporary, condition to you. For instance, the akashic download spell grants a +1 status bonus to a chosen Recall Knowledge check.
Penalties work very much like bonuses. You can have circumstance penalties, status penalties, and sometimes even item penalties. Like bonuses of the same type, you take only the worst all of various penalties of a given type. However, you can apply both a bonus and a penalty of the same type on a single roll. For example, if you had a +1 status bonus from an akashic download spell but a –2 status penalty from the sickened condition, you'd apply them both to your roll—so akashic download still helps even though you're feeling unwell.
Unlike bonuses, penalties can also be untyped, in which case they won't be classified as “circumstance,” “item,” or “status.” Unlike other penalties, you always add all your untyped penalties together rather than simply taking the worst one. For instance, when you use attack actions, you incur a multiple attack penalty on each attack you make on your turn after the first attack of the turn, and when you attack a target that's beyond your weapon's normal range increment, you incur a range penalty on the attack. Because these are both untyped penalties, if you make multiple attacks at a faraway target, you'd apply both the multiple attack penalty and the range penalty to your roll.
Once you've identified all your various modifiers, bonuses, and penalties, you move on to the next step.
This step is simple. Add up all the various modifiers, bonuses, and penalties you identified in Step 1—this is your total modifier. Next add that to the number that came up on your d20 roll. This total is your check result.
Whenever you attempt a check, you compare your result against the Difficulty Class (DC) of the check. Your check succeeds if it's equal to or greater than the DC. If you roll anything less than the DC, you fail.
Sometimes you'll know the DC and make the comparison yourself. Other times, you might not know the DC right away. Unlocking a looted comm unit would require a Computers check, but it doesn't have a specified DC—so how will you know if you succeed or fail? You call out your result to the GM and they'll let you know if it's a success, failure, or otherwise. While you might learn the exact DC through trial and error, DCs sometimes change, so asking the GM whether a check is successful is best.
When someone attempts a check against you, you might need to defend with one of your statistics that's normally a modifier, such as your “Reflex DC.” Rather than rolling a check of your own, you need to generate a fixed DC based on your modifier. Your DC for a given statistic is 10 + the total modifier for that statistic. So if you have a +4 Reflex save, your Reflex DC is 14.
Many times, it's important to determine not only if you succeed or fail, but also how spectacularly you succeed or fail. Exceptional results—either good or bad—can cause you to critically succeed or critically fail at a check.
You critically succeed when the check's result meets or exceeds the DC by 10 or more. If the check is an attack roll, this is also known as a critical hit. You can also critically fail a check. The rules for critical failure—sometimes called a fumble—are the same as those for a critical success, but in the other direction: if you fail a check by 10 or more, that's a critical failure.
Some actions and abilities have stronger effects on a critical success or failure. For example, a Strike deals double damage on a critical hit. If an effect doesn't list a critical success effect, the critical success effect is the same as the success effect, and the same goes for critical failures.
If you rolled a 20 on the die (a “natural 20”), your result is one degree of success better than it would be by numbers alone. If you roll a 1 on the d20 (a “natural 1”), your result is one degree worse. This means that a natural 20 usually results in a critical success and natural 1 usually results in a critical failure. However, if you were going up against a very high DC, you might get only a success with a natural 20, or even a failure if 20 plus your total modifier is 10 or more below the DC. Likewise, if your modifier for a statistic is so high that adding it to a 1 from your d20 roll exceeds the DC by 10 or more, you can succeed even if you roll a natural 1!
Certain abilities can change the degree of success on a roll. When resolving such an ability, apply the adjustment from a natural 20 or natural 1 before anything else.
Perception measures your ability to be aware of your environment. Every creature has Perception, which works with and is limited by a creature's senses. (Details on senses and detecting things begin here.) Whenever you need to attempt a check based on your awareness, you'll attempt a Perception check. Your Perception uses your Wisdom modifier, so you'll use the following formula when attempting a Perception check.
Perception check result = d20 roll + Wisdom modifier + proficiency bonus + other bonuses + penalties
Nearly all creatures are at least trained in Perception, so you will almost always add a proficiency bonus to your Perception modifier. You might add a circumstance bonus for advantageous situations or environments and typically get status bonuses from spells or other magical effects. Items can also grant you a bonus to Perception, typically in a certain situation. For instance, the retinal reflectors augmentation grants a +1 item bonus to Perception checks to Seek.
Circumstance penalties to Perception occur when an environment or situation (such as fog) hampers your senses, while status penalties typically come from conditions, spells, and magic effects that foil the senses. You'll rarely encounter item penalties or untyped penalties for Perception.
Many abilities are compared to your Perception DC to determine whether they succeed. As with any DC based on a modifier, your Perception DC is 10 + your total Perception modifier.
Often, you'll roll a Perception check to determine your order in initiative. When you do this, instead of comparing the result against a DC, the GM will put the results for everyone in the encounter in order. The creature with the highest result acts first, the creature with the second-highest result goes second, and so on. Sometimes you may be called on to roll a skill check for initiative instead, but you'll compare results just as if you had rolled Perception. The full rules for initiative are found in the rules for encounter mode.
Starfall has a variety of skills for many different situations, from Athletics to Computers to Piloting. Each grants you a set of related actions that rely on you rolling a skill check. Each skill has a key attribute modifier, based on the scope of the skill in question. For instance, Athletics deals with feats of physical prowess, like swimming and jumping, so its key attribute modifier is Strength. Computers deals with the ability to work with computer systems and other technological equipment, so its key attribute modifier is Intelligence. The key attribute modifier for each skill is listed in Chapter 4: Skills. No matter which skill you're using, you calculate a check for it using the following formula.
Skill check result = d20 roll + the skill's key attribute modifier + proficiency bonus + other bonuses + penalties
You're unlikely to be trained in every skill. As normal, when using a skill in which you're untrained, your proficiency bonus is +0; otherwise, it equals your level plus 2 for trained, or higher once you become expert or better. The proficiency rank is specific to the skill you're using. Aid from another character or some other beneficial situation might grant you a circumstance bonus. A status bonus might come from a helpful spell or magical effect. Sometimes tools related to the skill grant you an item bonus to your skill checks. Conversely, unfavorable situations might give you a circumstance penalty to your skill check, while harmful spells, magic, or conditions might also impose a status penalty. Using shoddy or makeshift tools might cause you to take an item penalty. Sometimes a skill action can be an attack, and in these cases, the skill check might take a multiple attack penalty.
When an ability calls for you to use the DC for a specific skill, you can calculate it by adding 10 + your total modifier for that skill.