D&D 5E Designing a dungeon for a big party

[Helldritch]

Ok, let's get down to this.
Both of my group are 6 players strong. Sometimes, these groups have NPCs going for them as henchmen rising up the party composition up to 12 (sometimes more...) All henchmen are played by the players and it takes a really special NPC for me to play it (usualy, it is only for the time it takes to establish its personality).
This means that I have some experience with large parties. Not on your scale but it can be useful nonetheless.

Here are my pieces of advice.

1) Take your turn or dodge.
If someone does not know what to do when his initiative count arrive, if he hesitate or worse takes too much time to think. Then the character simply take the dodge action. Go right to the next player. This will make sure that everybody is following the game and not something else (such as small talk or simply a radio song...). Surprisingly, this is especialy effective if a group nearly dies because of a dodge action that should not have been taken. The attention you will get at your table will increase tenfold.

2) Take no arguments at the table. Your ruling is non negotiable (at the table at least).
With that many players, arguments are doomed to slip in. Do not tolerate. Yes you might make a mistake. Yes you might have missed something. But in the end you have the final word. Make sure that your players understand that argument must not occur at the table. If you make a mistake, you can allow a player to wrest his case after the game. If he/she's right, then allow the player an inspiration for the next session and explain it to the group beforehand as to clear out any misunderstandings. The equivalent of a hero point could be appropriate too.

3) Give some players some responsibilities.
Have a player keep track of initiative order for you. One thing less to manage is good.
Have a player draw the tactical maps as you call the initiatives. One thing less to manage.
Have a player place the players' mini on the map. Again, one thing less to manage. Place the monsters/foes yourself.
Have an other player clean up the tactical map afterward.

4) More players can take on more challenges.
Obvious as it may be, it is easy to fall in the "Bigger challenge" trap where more players should be able take on more challenges. The 6-8 encounters per day might become 10 to 14! Restrict short rest periods to a maximum of 2. Make random encounters mean something. Be sure that if the alarm is sounded, that it will kill the group. This will keep them on their toes and it will force them to keep their ressources as much as possible.

5) Most of your adventures should be outdoors or in big areas.
Although it might be tempting to restrict the size of rooms to force a sense of tactics and realism. There is no fun in not being able to participate in a combat because you are outside the room. If this occur too often, you will see a lot of frustration.

6) Use Quickleaf other suggestions. They're perfect and I couldn't have done a better job in describing them.

I hope I have been useful.

 

[Reynard]

Could you explain why the strategy you tried to split the party didn't work? Was it because there was no time pressure so the PCs could just activate the "spell keys" and then the casters could return to the party and join them to pass the now-open door?

I did not put anything in the two unlocking rooms to held the casters and their bodyguards there, like a trap or a creature. So while the main body of the party found themselves facing some monsters in the freshly opened room, the rest of the PCs were able to join the situation in short order. had the unlock triggered 3 separate encounters I think it would have gone off better.

 

[Gene Sollows]

I've been running a large group for a over a year. It's a shared campaign where the DM has a character; we typically have 8-9 PCs per session, and we run for 4-6 hours per session. My players are all experienced gamers in their 40s+.

I have had my ass handed to me regularly by this party until I stepped up the difficulty. Basically I don't create any encounters that aren't at least 'hard,' and most are 'deadly.' I have found if I don't do this the fights are boring, few resources are used, and the players start taking ridiculous risks just to inject their own danger. THE PLAYERS HAVE TO RESPECT YOUR MONSTERS.

Simply put, the 'action economy' (there's a search term for you, I promise) of a larger group, combined with more players out-thinking you (as the DM) means they're going to do more on their turns than you are on yours. The players by early tier 2 (level 5-6) will mostly be AC 18+, have +8 or more to hit regularly, and be able to consistently deal good damage every turn to most of your monsters. The monsters in turn do not generally have very high ACs -- only 'boss' monsters have decent (18ish) ACs, the rest are typically in the 13-16 range.

You therefore need to get out your big damage and/or control effects early and often, because otherwise the fight will be over before it begins. This is of supreme importance when dealing with groups larger than 5 PCs.

Also in a large party you run into the initiative problem. If your monster(s) roll poorly, they will get pounded hard and fast and you may never get a chance to get out your cool monster abilities. Combats (even the big ones) usually only last 3-4 rounds against a large party. Your monsters have to "smoke 'em while they got 'em." Don't hold back or fudge for the players. Roll out front of the DM screen and make them feel the criticals. If you have an enemy wizard with fireball, cast it. If you can't bring yourself to do it, then don't put the monster in there. You have to be willing to kill some people from time to time and make them play smart and respect your monsters.

You therefore have to compensate by either setting the stage to give your monsters lots of advantages (e.g., flying monster, underwater encounter, separate the party, surprise, etc.) or simply hammer them with a big encounter with monsters that have complimentary abilities.

Here's a real life six-hour session with 17 (!) player-characters (it was the culmination of a story arc involving multiple PC groups converging on a common climax). The PCs were 3-6 level, though most were 4th or 5th.

Encounter 1: Giant Cave. 1 Gnoll Pack Leader, 1 evil Druid (upped to 9th level), 5 Fangs of Yeenoghu, 12 Gnolls, 14 Hyenas. The players were attacked from three sides.

This encounter lasted about 3 rounds. My monsters could barely touch the players. I was convinced that the Fangs would kill someone and maybe a hyena could do the gnoll transformation thing by feeding on the corpse. Not even close.

Encounter 2: Big crypt. 1 Mage (with Necro spells), 2 Wraiths, 10 Wights. This actually went pretty well for the monsters. I managed to kill a PC with a critical life draining attack from a Wraith after one of the clerics turned about half of them, and reduced the hit point maximums on a few other players. The mage's actions got sucked up dispelling the other cleric's daylight spells, so kudos to the PC for essentially neutralizing the BBEG.

Encounter 3: Massive Greathall. 1 Warlord, 1 Warpriest, 1 Master Thief (all from Volo's, some with extra stuff), 4 hill giants, 20 bandits, 4 thugs, 2 veterans. On paper this looked like I would annihilate them. But I knew better. Slow and Stinking Cloud controlled a few of the tough NPCs and giants early, and the low CR monsters were good mostly for absorbing the area effect damage spells. The giants did pretty good as meatbags but the party killed everything but the 3 NPCs who managed to retreat.

Initiative was key here. My Warpriest and Master Thief barely got in the fight due to early control by the PCs.

We crammed all three of those encounters into a 6.5 hour session without stopping. It's hard to get much done with a big group, even when your players are helping out (in ways already suggested here).

Some of the fun scene-setting, setup encounters just don't work as well with big groups. It's often easier to DM-fiat / "box text" through some of that stuff so that you can keep the group engaged in the next encounter.

RE: space requirements, to echo what others have written, you need adequate room to house such encounters. The standard 10x10 hallway and 30x30 chamber from 1st edition doesn't work with large parties, though I know Gygax routinely ran for large parties and didn't change a thing. I guess that's why everyone had a polearm, bow, and/or 10' pole.

I don't recommend giant groups except for fun massive battles from time to time. The RP, exploration, and other game elements are better with a group of 3-6 players. Everyone gets to be unique and have a chance to shine in a smaller group.

For this reason we're actually considering splitting the group into two tables, even though it takes another player out of rotation to be a DM.

Lastly, because of the sheer volume of class abilities and spells, you need to assume that your players will be able to access a multitude of bonuses for various skill checks. The PCs will be difficult to surprise, catch in traps, etc. So you either need to dispense with such checks or make them harder occasionally to give the rogues and scouts and sage types something to do out of combat.

 

[Imaculata]

One of the more interesting things you can do with such a large group, is create far more complicated encounters. You can force your players to divide their attention, by having multiple goals. This relates to puzzles, where the party has to complete various task simultaneously in adjacent rooms (a soft party split). But it also relates to battles, where you can ramp up the scale of the battle, and the number of goals that the party needs to worry about. This means you can (and perhaps should) make your battles about more than just defeating all the bad guys.

In my own campaign I had a situation where a big magic show in a bay, by a group of traveling wizards, was disrupted by evil cultists. First there was a giant explosion, and a VIP was mortally wounded. Then the cultists started firing randomly at the audience, causing a panic and a wave of people fleeing to safety. Meanwhile a massive coral golem had been summoned in the bay, and some of the cultists were unleashing some of the magical creatures that belonged to the traveling circus.

So the players had a lot of things to worry about. They wanted to get to the VIP as soon as possible, and hopefully save his life. But they also wanted to take out the cultists, and protect the fleeing audience. Lastly they had this giant Coral Golem to worry about, along with the escaping circus animals (some of which were very dangerous, such as a giant black scorpion). The water of the bay created a natural barrier, with the Golem right in the middle of it. Since the players were sitting on opposite ends of the show, this was a soft party split. They were divided within the same large location.