Does a single PC who is stealthy get to surprise monsters when the rest of the group is not?

Question

The rules for a surprise round, seem to be focused on the people being surprised. (They lose a turn) rather than being focused on the people doing the surprising (They get an extra turn)

The rules are clear, that each person in a group can be surprised, even if other people in the group are not surprised. So if a party is ambushed by a single stealthy carrion crawler, some members of the group will lose a turn (be surprised) and others will not (they get to act normally).

However, I'm not clear what happens if two groups approach each other, were some members are being stealthy and others are not.

For example, I have a Rogue who is being quiet and stealthy and rolls a 20 on their stealth check. The rest of the group however (Fighter and Wizard), is just marching along at a slow pace. They turn a corner, and see a group of 4 goblins, with a passive perception of 13. Do the 4 goblins lose their first turn because they are surprised by the rogue? Do the Fighter and Wizard get to act on that first turn?

Another example, Same two groups. Two of the goblins rolled a 20 on their stealth, and the other two rolled a 5. Are the Fighter and Wizard and Rogue surprised? (They lose their first turn) Or can they only attack the two goblins with a stealth of 5?

Answer 1

Surprise and stealth seemed to be explained in better detail in the Starter Kit

The Lost Mine of Phandelver features a small goblin ambush (as seen in the WOTC Livestream). The rules walkthrough for the stealth check and the suprise round says to roll once for all the goblins (adding their +6 stealth skill) and compare that one, party-wide check to Passive Perception of the PCs. PCs whose passive is less than the goblin stealth check are surprised and do not act in the first round.

This concurs with the Basic rules where in general one part or the other has the possibility of surprise depending on who is trying to set up an ambush.

1 player/PC scouting ahead of the main party would be treated like a separate party for the purposes of surprise round. They might find some goblins, fail to be noticed by the goblins, slip away warn the party, then the party as a whole could try to stealth forward.

A player showing up late to a fight could be hidden if they make a suitable stealth roll (i.e. some kind of cover) giving them advantage.

In combat, most creatures stay alert for signs of danger all around, so if you come out of hiding and approach a creature, it usually sees you. However, under certain circumstances, the Dungeon Master might allow you to stay hidden as you approach a creature that is distracted, allowing you to gain advantage on an attack before you are seen.

If the monsters and the main bulk of the party have already spotted one another/are engaged in combat I don't think a player who is further behind would in anyway get a surprise round compared to everyone else, no matter how good their stealth check. The enemies have already been alerted to the presence of the party (their enemies) and will be wary as the combat commences.

However if that player is trying to sneak into the combat, they can and should get advantage if they make a good enough stealth check.

Answer 2

Now that the rulebooks have been published, we have a much clearer answer to this question.

From Chapter 9: Combat, under Surprise:

Any character or monster that doesn’t notice a threat is surprised at the start of the encounter.

If you’re surprised, you can’t move or take an action on your first turn of the combat.

Thus we can see that losing your first turn or not has nothing to do with your own Dexterity (Stealth) result, and everything to do with your Wisdom (Perception) result.

So, in your first example, with 4 non-stealthy goblins (passive Perception 13) vs. a stealthy Rogue and a non-stealthy Fighter and Wizard: The goblins detect the Fighter and Wizard, and the party detects the goblins. Since everyone detected at least one threat, no one is surprised, and no one loses a turn.

In your second example, where two goblins rolled high for Stealth and two rolled low (N.B. the DMG advises one roll for the whole group of identical monsters, but of course, if the DM chooses to make separate rolls, it's their prerogative): the PCs notice the poorly-rolling goblins, so they are not surprised, and do not lose a turn.

An additional point to consider:

There are two alternative methods for handling the party's stealth checks, but the rulebooks don't explicitly define which situations are eligible for these methods, so it's up to the DM to decide which, if either, of these can be applied for stealth checks. But since, without using them, any PC that fails to be stealthy spoils the chance for surprising the enemy, either one would be an improvement over a group of PCs in which one or more make no efforts to be stealthy. Both of these are described on page 175 of the PHB:

• Working Together:

  Sometimes two or more characters team up to attempt a task. The character who’s leading the effort—or the one with the highest ability modifier—can make an ability check with advantage, reflecting the help provided by the other characters. [...]a character can help only when two or more individuals working together would actually be productive.

  (Personally, I don't consider this one applicable to stealth checks.)

• Group Checks:

  When a number of individuals are trying to accomplish something as a group, the DM might ask for a group ability check. In such a situation, the characters who are skilled at a particular task help cover those who aren't. To make a group ability check, everyone in the group makes the ability check. If at least half the group succeeds, the whole group succeeds. Otherwise, the group fails. Group checks don’t come up very often, and they’re most useful when all the characters succeed or fail as a group.

In lieu of either of those options, a party that wishes to avoid ambushes should at least do one of these two things:

• Have the stealthy Rogue scout a bit ahead of the Fighter and Wizard.

• Have the Fighter and Wizard make stealth checks, even if they do have poor modifiers.

By staying close to the Rogue and making no attempt whatsoever to be quiet, the Fighter and Wizard completely nullify any such efforts on the Rogue's part.

Answer 3

You are surprised if you don't notice a threat

The rules for surprise state that you only have to notice a threat in order to not be surprised:

Any character or monster that doesn't notice a threat is surprised at the start of the encounter.

If you have successfully hidden, then you are undetected

Even if a monster notices someone else in your party, if they have not beaten your Stealth check with their Perception check, then you remain hiding:

Until you are discovered or you stop hiding, that check's total is contested by the Wisdom (Perception) check of any creature that actively searches for signs of your presence.

Example 1

A stealthy rogue rolls a 20 on their Stealth check. The rest of the group is not stealthy. The group encounter 4 goblins with passive Perception 13, the goblins cannot detect the rogue, but they can plainly see the fighter and wizard.

• The goblins are not surprised since they can detect the fighter and wizard.
• The rogue, fighter, and wizard are not surprised since they can detect the goblins.
• The rogue remains hidden - unseen, unheard, and unlocated, and unless the goblins already know that the party contains 3 members, then they are completely unaware of the rogue.

What would be a better plan for the party? Have the rogue scout ahead to locate enemies and initiate combat.

Example 2

The same two groups, but this time two goblins rolled 20 on their Stealth.

• The goblins are not surprised since they can detect the fighter and wizard.
• The rogue, fighter, and wizard are not surprised since they can detect 2 of the goblins.
• The rogue remains hidden - unseen, unheard, unlocated, and unless the goblins already know that the party contains 3 members, then they are completely unaware of the rogue.
• The 2 stealthy goblins remain hidden - unseen, unheard, and unlocated, and unless the party already know that there are 4 goblins, then they are completely unaware of the 2 hidden goblins.

Example 3

The same two groups, the rogue rolls 20 on their Stealth check and the rest of the group is not stealthy. The rest of the party stay out of range, while the rogue starts the fight.

• The goblins are surprised since only the rogue is fighting, and the rogue's Stealth roll was too high.
• The rogue is not surprised since they can detect the goblins.
• The rogue is hidden - unseen, unheard, and unlocated, until they do something to reveal themselves.
• The rest of the party remain unknown to the goblins until they enter the fight.