D&D 5E Monster group stealth

[Springheel]

I'm helping a new DM learn the 5e rules, and I'm not sure I gave him the right advice last night. Assume the following scenario:

A green hag and 4 bullywugs are lying in wait in a dimly lit temple. They plan to hide and ambush the unaware players as they enter. How many stealth rolls should the DM make? Does each creature make it's own stealth roll? It seems likely that at least one will roll poorly if so. Does the DM make a group check with all the creatures? Does he roll individually for the hag and a group check for the bullywugs? Does he roll once for the hag and once for the group of bullywugs?

I told him to do the last one, though I'm not sure that was correct (I think I was thinking of initiative).

He rolled a 12 and 13. Not very impressive rolls.

However, since none of the players were looking for trouble, and the temple was dimly lit, their passive perception was less than 9, so they didn't see any of the opponents and were surprised.

 

[John R Davis]

In that situation Id assume the monsters have 10+lowest stealth and compare to passive perception. If the monsters have really really had time, planning, resources to hide assume they did it advantage so really 15+ lowest stealth
Simple

 

[Springheel]

Why wouldn't you roll the dice?

 

[FormerlyHemlock]

I'm helping a new DM learn the 5e rules, and I'm not sure I gave him the right advice last night. Assume the following scenario:

A green hag and 4 bullywugs are lying in wait in a dimly lit temple. They plan to hide and ambush the unaware players as they enter. How many stealth rolls should the DM make? Does each creature make it's own stealth roll? It seems likely that at least one will roll poorly if so. Does the DM make a group check with all the creatures? Does he roll individually for the hag and a group check for the bullywugs? Does he roll once for the hag and once for the group of bullywugs?

I told him to do the last one, though I'm not sure that was correct (I think I was thinking of initiative).

He rolled a 12 and 13. Not very impressive rolls.

However, since none of the players were looking for trouble, and the temple was dimly lit, their passive perception was less than 9, so they didn't see any of the opponents and were surprised.

My advice: use the same rules for monsters and NPCs that you do for PCs.

Group stealth checks are simple, but have the potential to become horribly broken (as in, a dominant strategy). If you roll stealth individually for each creature, you're making stealth something that only small bands of creatures can do well--large groups will always have someone give themselves away. That leads to a pretty good game, especially if the players think there's only one bullywug and then suddenly three more bullywugs and a green hag hit them from behind.

 

[MechaPilot]

I'm helping a new DM learn the 5e rules, and I'm not sure I gave him the right advice last night. Assume the following scenario:

A green hag and 4 bullywugs are lying in wait in a dimly lit temple. They plan to hide and ambush the unaware players as they enter. How many stealth rolls should the DM make? Does each creature make it's own stealth roll? It seems likely that at least one will roll poorly if so. Does the DM make a group check with all the creatures? Does he roll individually for the hag and a group check for the bullywugs? Does he roll once for the hag and once for the group of bullywugs?

I told him to do the last one, though I'm not sure that was correct (I think I was thinking of initiative).

He rolled a 12 and 13. Not very impressive rolls.

However, since none of the players were looking for trouble, and the temple was dimly lit, their passive perception was less than 9, so they didn't see any of the opponents and were surprised.

You really have a few options. for how to handle it.

1) every creature rolls for individual success or failure.
2) roll once for all creatures and determine success or failure based on individual bonuses.
3) have the creature with the worst modifier roll to determine if all succeed.
4) every creature rolls and majority rules (more successes than failures = hidden, more failures than successes = not hidden)

My advice: use the same rules for monsters and NPCs that you do for PCs.

When it comes to determining how to resolve something, I think treating PCs and monsters the same is the best rule.

 

[Shiroiken]

In general, I don't actually roll stealth very often. Usually I set a DC based on the monster's average Stealth, then tell the party to roll Perception. The roll doesn't take place until it's too late to change anything, and is often used only to determine surprise. If I feel there is a reason why the PCs should suspect an enemy before it's too late, then I'll make the roll (usually before the session) by monster groups (because I'm lazy).

 

[fjw70]

I would roll once for the hag and once for the bullywugs. For PCs I always have each PC roll. A weak link makes for good stories.

 

[ClearlyTough69]

It's striking that every answer is different. And so's mine! But it's close to the answer you gave.

I'd roll Stealth for the hag, and Stealth for the bullywugs separately. Because they have time to prepare the ambush they roll with advantage.

I would use each PC's passive Perception to determine if he/she is aware of or surprised by the hag on the one hand and the bullywugs on the other. The dim light would impose disadvantage on the Perception check of any PC without darkvision, or if the encounter starts with the ambushers out of range of darkvision.

 

[Rhenny]

In general, I don't actually roll stealth very often. Usually I set a DC based on the monster's average Stealth, then tell the party to roll Perception. The roll doesn't take place until it's too late to change anything, and is often used only to determine surprise. If I feel there is a reason why the PCs should suspect an enemy before it's too late, then I'll make the roll (usually before the session) by monster groups (because I'm lazy).

I usually set DC as well especially if the creatures have had time to actively hide or set up an ambush. But sometimes I roll. As a DM, I like variety too. Since most of my games are via Fantasy Grounds, it is not as difficult to roll for each monster, but if there are a ton of them, I will most likely just set a group dcs, sometimes by location so if there are 3 to the left, 3 to the right, 3 in front, etc, I'll roll foe each grouping.

 

[Saeviomagy]

How I do it:
I always endeavor to have only one party make rolls. Rolling 1D20 is swingy enough. Rolling 2 is ridiculous, diminishing typical

I always choose who rolls what based on the range of possible outcomes. In this case, the monsters being spotted before the ambush happens is binary, and ideally having a small group of ambushers should be feasible. That rules out having each player roll vs each monster: the result of doing so will almost always be a failure to ambush, which is ridiculous.

In this situation the PCs will take their passive perception as their perception score - which also means I don't need to tell them anything that might change their behaviour. Note that depending on situation, certain members of the group are supposed to have their perception scores ignored or reduced... but I personally find those rules to be ridiculous, and assuming the passive scores also makes them someone redundant: you're simply assuming the character with the highest perception will be the lookout.

I only have to look at the highest passive score. The monsters need to roll, however having them all roll basically means that the chance of 4 monsters succeeding at an ambush is vanishingly slim, even if they're good at hiding. To me, that's a ridiculous outcome. Instead I use a (modified) group check. Roll each monsters skill, the result of the check is the median result (ie - you roll all the checks, arrange them from lowest to highest, then take the middlemost result OR the average of the two middlemost results). This is to determine whether an ambush happens at all.

But what if there's an entire army, I hear you say? Shouldn't they have less chance to perform an ambush? My reply to that is that if you've got an entire army in an ambush position over a rise, then yes, they can perform an ambush without ending up with a DC of 1 + lowest member's stealth score. That's why armies have scouts.

Once you've determined that an ambush happens, the surprise round is done in reverse: the players are now the ones who roll their perception score, and they do so vs the monster's lowest passive stealth. This establishes who is surprised.