How to handle large groups of enemies?

Question

A week ago for my Friday night session, my adventurers came across a pack of 18 Gnolls. 16 of them were your basic Gnoll fighter, one was a Gnoll Pack Leader, and the last was a Gnoll Fang of Yeenoghu (which was responsible for the rapid multiplying of the Gnoll Population).

I had planned that the group would meet these 18 Gnolls in 3 separate encounters, such that the group would only face six at a time. But the group decided to enter their area from 3 sides and, lo and behold, activated all 3 groups at once.

The Initiative order of 18 Gnolls plus my players was so extensive that one of my players fell asleep before his turn came around again (It was about 1am by that time). The next day me and one of the core players reflected a bit and it was brought to my attention that the encounter could have perhaps been handled differently.

What is the best way to I handle large creature counts?

While I am aware that I could create 3 enemies representing a group of Gnolls each, each a single mechanically strong enemy to ensure the encounter is just as hard, this does not give the right atmosphere if I want my players to feel overwhelmed by a multitude of lesser creatures. How do I give this overwhelming feeling, without an initiative round lasting for hours?

Answer 1

A few suggestions, apply those that sound fun to you:

1. Group creatures of the same type into a single initiative number. Or at least, put a good chunk of them to act on the same initiative.

2. Maybe don't act with all creatures. Some are probably stuck way on the back and do not get a piece of the action until the adventurers mow their way into them.

3. For each chunk of equal creatures, pick a group of targets, grab a handful of dice and roll their attacks all at once. Serves to drive up the point of their numbers.

4. Spend most of your time narrating during the player's turns, talking about their actions. Be less descriptive about mob attacks.

5. Add the mass of creatures to an encounter where something else needs to happen, not just kill them all. For example, the adventurers need to get to the other side of a large battlefield, not necessarily defeat everyone on their way there.

6. Enlist another player to keep track of the enemy hit points or the initiative rooster (maybe one for each). By splitting tasks, long battles are made shorter.

7. Make smaller minions die faster (give them less HP, instead of rolling dice or using the half + 1 suggestion, just use something smaller if they are disposable). Or make them retreat when weakened, which maybe allows adventurers to sneak in some opportunity attacks, ie. stuff to do while they wait for their turn.

Answer 2

I can give you an example of something I've done (in 5E no less). Its not perfectly balanced, I suspect it leaned a bit towards favoring the players, but it got the job done in a way that I was satisfied with.

• Combine them into groups of four (or five, that seemed to work out well). Move them around as if they were a single Large creature (2x2 tiles on a grid). Stop thinking of them as separate creatures.
• Let this "new" creature take two turns, and let all its' attacks always have Advantage.
• Let this "new" creature have hit points equal to half the amount the creatures would have had before being combined.

Reducing the hit points so severely might seem unbalanced, but the idea here is that the "new" creature is still going to be taking two turns with Advantage even when its hit points are low (which would normally mean dead creatures with fewer actions to take.) This sort of thing was inspired by my experience with Numenera, which has much simpler rules for monsters such that combining them into one group is quite easy.

Note: While I love the idea of giving individual enemies their own initiative, I've found this to rarely be enjoyable in practice. Its easier to let all monsters act at the same time, though occasionally it may be worth letting spell-casters or important monsters have their own initiative count.

Answer 3

In the 5e DMG pg 250 it mentions Handling Mobs. It offers a table with which you determine the d20 roll required to hit a player (attack bonus - AC). This number determines how many attackers are needed for one to hit (refer to the table).

Here is a related post: DMG: page 250 as a complete mass combat system

For example, let's say you have a hoard of 20 archer goblins all taking aim at the paladin that just entered a large chamber. The goblins have +5 to hit and the paladin has an AC of 18. This means that the d20 needed to hit the paladin is 13 (AC- hit bonus). The table states that if a 13 is needed to hit, it requires 3 attackers to make one hit. Now divide the 20 goblins by the 3 required to hit, and you have 6 successful hits. Just roll 6 damage rolls and you're done!

Answer 4

Dungeon Master's Guide: Mob Combat

Group them into the same initiative, subtract their attack bonus from the target's AC then use that number to refer to the table below to determine how many of their attacks hit the target.

DMG Page 250:

Instead of rolling an attack roll, determine the minimum d20 roll a creature needs in order to hit a target by subtracting its attack bonus from the target's AC... The table shows you how many creatures that need that die roll or higher must attack the target in order for one of them to hit...If the attacking creatures deal different amounts of damage, assume that the creature that deals the most damage is the one that hits...This This attack resolution system ignores critical hits in favour of reducing the number of die rolls.

d20 Roll Needed	Attackers needed for one to hit
1-5	1
6-12	2
13-14	3
15-16	4
17-18	5
19	10
20	20

I know that this post is hell old but it still popped up while I was googling for an answer to this. Thought I'd share for anyone else who needs it, especially because these are the official rules.

Answer 5

Unearthed Arcana: Mass Combat Rules

I haven't tried this in my D&D 5e game, but it seems to fit your needs so exactly that it would be a shame not to offer it up. As part of the D&D Unearthed Arcana series, Wizards of the Coast offer some free Mass Combat rules.

From the promo text:

In this second installment of Unearthed Arcana, we build on the standard combat rules to model conflict on a much larger scale, allowing players and DMs to control whole armies. At the same time, these rules for mass combat allow individual adventurers to lead an army’s charge against an enemy regiment, rally dispirited soldiers to rejoin the fray, or defeat powerful enemy monsters or leaders.

Of relevance to your situation, the rules separate between solos (ie PCs) and stands (ie groups of 10 enemies), which seems to fit the scale you describe. There are also rules for units (groups of stands), but that then goes beyond 'skirmish' and into 'mass battle' territory. However, the rules as such can be used for skirmishes on the scale you describe, and will almost certainly run more quickly than managing everything in individual scale.

Note: These rules are more or less at 'beta' level, but still worth a shot as they come from the publishers of the game, and they're free of charge. The fact they're specifically designed for 5e is also speaks in their favour.