Skills have seen a wide variety of approaches over the years. The earliest forms of D&D tended to only have formal mechanics for the functions of the thief, but the role of mechanisms for overcoming non-combat challenges have expanded since then. The current skill system is relatively pared down and uses a simple resolution system.
D&D 5E uses the Ability Check as the basis of its system. All ability scores (Strength, Dexterity, Constitution, Intelligence, Wisdom and Charisma) have an ability modifier which typically ranges from -1 to +5 for a player character. By rolling a d20 and adding the modifier, you can attempt to hit a target number; either one set by the DM or one rolled by an opponent.
Each character has several areas they are considered proficient in and, in these, they get an additional proficiency bonus which ranges from +2 to +6 depending on their level. As a result, if a character is proficient in something, the modifier will range from +1 to +11.
Armour Proficiencies just allow you to employ the armour. All other proficiencies allow you to add your proficiency bonus and your ability modifier to your roll.
The Difference between Ability Checks, Saving Throws and Attack Rolls
Although the mechanics of determining your modifier for an Ability Check, Saving Throw or Attack Roll are basically identical, the three types of check are considered different in the rules. An Ability Check includes Skill and Tool use, but if a special power gives you a bonus to Ability Checks, it does not also apply to Saving Throws or Attack Rolls. This is an important distinction to remember.
Skills and Tools
The intention of 5E is to have skill proficiencies and tool proficiencies with little or no overlap. Instead of being proficient in Open Locks, you are instead proficient in Thieves’ Tools, which allow you open locks and disable traps. Tools such as Mason’s Tools take the place of the crafting skills of 3E.
Tools are not tied to a particular ability modifier, whereas Skills normally are. You might use Dexterity or Strength whilst using Woodcarver Tools, but you will almost always use Dexterity when using Stealth. (An optional rule suggests using other ability scores for some skills when appropriate).
Characters begin the game with a number of proficiencies in weapons, armour, skills and tools through their race, background and class. When you are selecting proficiencies, you can’t select the same one twice to get double the benefit. You are either proficient in something or not. Certain classes (like the Rogue) have ways of improving their skill use (see Expertise, below).
Backgrounds typically give you two skill proficiencies and possibly one or more tool proficiencies. Classes give you a list of skill proficiencies from which you can select two more (not the same you gained from your background!)
It is possible to train to gain proficiencies in tools – see the Downtime Rules in the Adventuring Chapter of the Basic D&D pdf. It takes 250 days and 250 gp. You can also learn languages using this procedure.
The rogue has an additional ability known as Expertise, which allows him or her to double the proficiency bonus. This means that a rogue in their chosen skills will have a modifier of +3 to +17. This is a significant bonus. (It is also slightly lower than the bonus in the playtest, which was a flat +5).
The number you need to roll to succeed at a check is known as the Difficulty Class. For attack rolls, the DC is the Armour Class of the target. For saving throws, the DC is the spellcasting DC of the spellcaster.
For ability checks, the suggested DCs are listed on page 58 of the Basic D&D pdf (version 0.1) and range from 5 (Very Easy) to 15 (Medium) to 30 (Nearly Impossible). An examination of the bonuses typical for normal ability checks, proficient ability checks and expertise ability checks will quickly show that it is a lot harder to succeed if you don’t have at least proficiency in the check.
As a result, the DM will need to be careful when setting DCs. A DC of 10-15 would be adequate for most uses, with 20 and above being reserved for exceptional use. It is notable that the Basic D&D pdf does not give sample DCs for tasks and just relies on the generic table.
Setting high DCs for checks where no skill or tool apply is likely to cause frustration for the players, although a DM should always do so when the task is actually hard or impossible. However, a DC of 15 is going to be very difficult to reliably achieve with just the ability score modifier.
Opposed Checks just compare the roll between two opponents with either the same skill or opposed skills (Stealth against Perception, for instance).
Each character class has two saving throws with which they are proficient. These saving throws get better as they go up in level, but the other categories do not. This may lead to the situation where a Rogue has a +11 saving throw for Dexterity but a -1 saving throw for Wisdom. With the DC of spells ranging (typically) from 13 to 19, this indicates that high-level characters are likely to be extremely vulnerable to spells targeting their weaker saving throws.
In AD&D, characters get more resistant to spells as they gain levels – so much so that it is rare that a spell affects a high-level character fully. 3E changed that to make high-level spells harder to resist, and the mathematics worked so that it was very hard to resist the more powerful spells. In 4E, the power of saving throws was fairly constant throughout the levels – as the spells got more powerful, so did the resistance. The new D&D seems to cleave more to the 3E way of doing things.
To give a more 4E version, apply the proficiency bonus to all saving throws, using double the bonus with those saves you are proficient. A high level character will have a +5 in a poor ability score, so they’ll still fail much of the time against a DC 19 spell, but they do have some chance of success. Characters can fail against high-level spells they’re resistant against, but rarely.
To give a more AD&D version, use the method for 4E but set the DC of all spells at 15, regardless of spell-caster ability scores or proficiency. This has the side-effect of frustrating high-level casters.
Unlike the other forms of proficiency, Armour Proficiency allows you to wear armour without penalty and does not modify ability checks.
If you are not proficient in the armour you are wearing, you cannot cast spells and you have disadvantage on Dexterity and Strength checks, whether Attack Rolls, Ability Checks or Saving Throws.
It is worth emphasising that you are able to cast spells when you are wearing armour you are proficient in. In AD&D, magic-users could not cast spell in armour unless they were multi-class characters. In 3E, wearing armour gave the potential to fail to cast arcane spells with a percentage chance of failure, although there were ways around that restriction. In a lot of ways, this actually works a lot more like AD&D.
The Proficiency Bonus
It is worth listing what the proficiency bonus is applied to:
- Attack rolls with weapons you are proficient in
- Attack rolls with spells you cast
- Saving Throws where you are proficient
- Ability checks where you are proficient in the tool or skill being used
- Saving Throw DCs for spells you cast
At present, these are the only instances of the bonus being applied.
Passive Perception and Passive Checks
To save time (or because the DM doesn’t want the players to know something is going on), occasionally passive skill checks are called for.
A passive check assumes the character or monster rolled a 10. This is most commonly used with Wisdom (Perception).
A standard Wisdom (Perception) roll is 1d20 + Wisdom modifier + proficiency bonus if proficient.
Thus, the Passive Perception number is 10 + Wisdom modifier + proficiency bonus if proficient.
Alternatively you could express it as 10 + Wisdom (Perception) bonus.
Note that expertise in Perception may double the Proficiency Bonus, so Rogues who are expert at Wisdom (Perception) can be very hard to surprise indeed! (The Alert feat also applies; potentially, a 20th level rogue with 20 Wisdom, expertise in Perception and the Alert Feat would have a +22 Perception modifier and a 32 Passive Perception!)