Is skill check always against a DC or why is stealth an exception?

Question

I'm a little bit confused about skill checking. I'm reading through LMoP and in the first goblin encounter, the adventure suggest the goblins make stealth check against PCs passive perception.

Then later, I'm reading about the nothic encounter from which I understand the creature can be intimidated or persuaded to cooperate or tell what it knows. For this, players would have to make persuasion/intimidation check. But this is where I'm a bit confused - players make skill checks agains what? DC set by a DM? Or nothic makes a charisma saving throw when someone tries to persuade it? Or is it DC simply because nothic "doesn't know in advance" they're trying to persuade it so it can't make a saving throw against it?

I simply don't understand why with stealth there's a contest stealth/passive perseption and persuasion should simply be against DC set by a DM?

Thanks for any answers!

Answer 1

Don't overthink this

Breathe easy - you cannot do this wrong. Some DMs will favor ability checks over contests and some will lean more heavily on passive over active checks: each of these DMs is playing the game by the rules because "the DM decides what happens".

How to Play

First of all, focus on the fundamental rule of D&D 5e:

1. The DM describes the environment.

2. The players describe what they want to do. ...the DM decides what happens, often relying on the roll of a die to determine the results of an action.

3. The DM narrates the results of the adventurers’ actions.

(PHB p.6 "How to Play", paraphrased)

Note that rolling an ability check is never a requirement. In general, ability checks are only called for where:

• the result is uncertain. Convincing the nothic to do what it wants to do doesn't require a roll. And
• failure is an option. That is to say, failure presents new and interesting options to the players that are significantly different to what success would provide. Failing to convince the nothic not to eat you is going to lead to a combat which is different from not having a combat. And
• there are no re-runs. If the characters' can just keep trying until they succeed then just let them succeed. Failing to convince the nothic not to eat you means that its going to try and eat you right now.

Ability Checks versus Contests

Page 174 of the Player's Handbook calls out the distinction between an ability check which is made against a DC set by the DM and contest where each creature makes an opposed ability check.

Ability Check

For every ability check, the DM decides which o f the six abilities is relevant to the task at hand and the difficulty of the task, represented by a Difficulty Class.

Contest

Sometimes one character’s or monster’s efforts are directly opposed to another’s.

Both participants in a contest make ability checks appropriate to their efforts. They apply all appropriate bonuses and penalties, but instead of comparing the total to a DC, they compare the totals of their two checks. The participant with the higher check total wins the contest. That character or monster either succeeds at the action or prevents the other one from succeeding.

It is worth noting that the outcomes of contests are more random since they involve at least 2 rolls (more if advantage/disadvantage).

Passive Checks

In addition to that, p. 175 introduces the idea of a passive check:

A passive check is a special kind of ability check that doesn’t involve any die rolls. Such a check can represent the average result for a task done repeatedly, such as searching for secret doors over and over again, or can be used when the DM wants to secretly determine whether the characters succeed at something without rolling dice, such as noticing a hidden monster.

The goblins

The author is suggesting:

1. A contest: the characters' Wisdom (Perception) is being opposed by the goblins' Dexterity (Stealth).

2. A passive check: presumably because this is specifically the example given as to when these are appropriate, "noticing a hidden monster".

Equivalently, the DM could call for the players to make an active Wisdom (Perception) check and use the Goblins' passive Dexterity (Stealth): this is mechanically equivalent. Note that an active vs active check is not mechanically equivalent - an active check improves the characters' chances by 2.5%.

The advantages of the author's suggestion are:

• the player's remain in ignorance of why the DM is rolling dice - this can ratchet up tension if you get in the habit of occasionally rolling the dice and making "hmmmm" noises even when there is nothing to roll for. In contrast, asking the players' to make a Wisdom (Perception) check clue them into the fact that there may be something they are missing - unless you also occasionally call for these for no reason as well.
• Active checks are appropriate when the characters are being, well ... active. Be alert for when this happens "I look into the bushes" should trigger an active check. Active checks should never give worse results than a passive check: actively looking for you missing sock is not going to decrease the chance that your eye will light on it by chance.

The nothic

Is a roll called for? If the characters offer the nothic what it wants at trivial cost why would you roll? Other than the fact that the damn thing is insane and you may want to model this with randomness.

What you should determine is if this is a contest or not. It becomes a contest when "one character’s or monster’s efforts are directly opposed to another’s". In a negotiation this is not, or not necessarily, the case. If you decide that it is a contest then a Charisma (Persuasion) by the character is opposed by a Wisdom (Insight) by the nothic with advantages/disadvantages applied depending on the inclination of the nothic to do what they want anyway. If you decide that it isn't then just set a difficulty representing how hard it is to persuade and insane creature to do whatever is being asked.

Passive checks are inappropriate here.

Generalizing

• Don't roll unless you have to.

• A contest is appropriate when there is active opposition and the skill of the opponent is relevant to the outcome. For example a Charisma (Deception) check is more likely to be a contest then a Charisma (Persuasion) check.

• Passive checks are appropriate where a creature is not actively engaged.

• If there is a passive check and an active check it is irrelevant which is which. An active Dexterity (Stealth) check vs a passive Wisdom (Perception) is exactly the same as a passive Dexterity (Stealth) check vs an active Wisdom (Perception). This allows you to let the most appropriate person roll the dice: the DM if you are keeping secrets or the players if you want them more engaged in the outcome.

Answer 2

No. Some skill checks are resolved as contests instead of by DC

See page Contests on 238 of the DM Guide:

A contest is a kind of ability check that matches two creatures against each other.

Stealth seems to work differently than, say, picking a lock, because there are two creatures working against each other.

In this case, they both get to roll an appropriate skill check. Bonuses and penalties (including perhaps advantage/disadvantage) are applied, and the final numbers compared to see who wins.

NOTE: Stealth checks can also be resolved by comparing the stealth roll against the Passive Perception of the target, at the discretion of the DM. (In these cases, the Passive Perception score of the target functions as a DC.) This is often done when the “perceiver” is not actively on the lookout.

Answer 3

The examples given in the PHB (ca. p.174) are a subset of the guidance given to DMs (ca. p.237). They fall into three categories. Or two, depending on how you count. I'll say three. What follows is a distillation of those two sources.

1. Skill/ability check vs. "static" DC

GM sets a Difficulty Class, determines relevant ability score, proficient skill (if applicable), and player rolls check.

Classic examples: pry open a door, pick a lock, notice a fake book on a shelf....

2. Skill/ability contest vs. active skill/ability opposition

GM decides on relevant skill/ability, both player and GM (or other player, if PvP) roll check.

Classic examples: grapple=athletics vs. target's athletics or acrobatics; sneaking=stealth vs. perception; prevaricating=deception vs. insight....

3. Skill/ability contest/check vs. passive skill/ability opposition

This exists in a boundary area between the first two. Your active efforts are represented by your skill/ability check, opposition isn't a DC set by the GM, but isn't a GM roll, either: it's a passive check (10+relevant modifier(s)).

Classic examples: your attempt to persuade a bored (by you) guard might be an active persuasion check vs. the guard's passive wisdom or charisma. Or your sneaking past a guard might be an active stealth vs. a guard's passive perception.

In summary, here's how I suggest you think of it:

1. Players wish to achieve something. (Pry open the door, sneak past the guard, persuade the nothic to help.)

2. GM decides

   a. If it's impossible or

   b. if it's trivial;

   in either case narrate the result and move on.

3. If there's some chance of interesting failure and GM decides to use skill/ability check to resolve it, players narrate/GM interrogates until it's clear which ability/skill and what circumstantial modifiers might come into play. This check will go against

   a. a static DC if the "opposition" is inanimate/unaware/otherwise uninvolved in resisting (like the door being pried);

   b. a passive skill/ability score if the "opposition" is unaware/otherwise disengaged from the process (like a bored guard an hour from end of watch);

   c. an active skill/ability check if the "opposition" is actively engaged in the process (like the nothic who needs convincing).

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Further Reading:

DMG pp.237-240, "Using Ability Scores"

Angry GM's 5 Simple Rules for Dating My Teenaged Skill System (Warning: Angry GM's excellent analysis and commentary is liberally seasoned with rude and vulgar language.)