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Use a Damage Pool for Lots of Monsters

by Mike on 28 August 2023

Sometimes, when running lots of monsters, it's a pain to track the damage done to each monster. Thus, GMs don't tend to run more than six to eight monsters at a time.

But some of the best fantasy fiction focuses on a small band of heroes facing overwhelming odds. It's a staple in the genre and we want to have that option available to us when running our game.

One tool to manage this problem is the "damage pool" – an easy way to track damage being done to as many monsters as you want to throw at the characters. This trick is one part of a larger set of guidelines for running hordes available in the Lazy DM's Companion.

For a video on this topic, see my YouTube video on Running a Damage Pool for Lots of Monsters.

Track Damage in a Damage Pool

Here's how a damage pool works:

Instead of tracking damage done to individual monsters, track damage done to the whole monster group in a single tally – the damage pool.
Each time the damage pool takes enough damage to kill a single monster, remove the last monster hit and reset the damage pool to zero, rolling over any remaining damage.
Round each monster's hit points to the nearest 5 or 10 so the math is easier.
If you're running combat in the theater of the mind, track the number of total monsters. Remove monsters from this number as they're killed. If using tokens or miniatures, use the tokens or minis to track the number of monsters.
If a creature takes enough damage to kill multiple monsters in group, remove multiple monsters and narrate how the attack kills those extra monsters. Remove whichever monsters you want. Reset the pool.
If the horde gets hit with an area of effect doing enough damage to kill a single monster, remove all of the monsters hit by the spell.
If the group gets hit with a smaller area of effect spell, like burning hands, multiply the damage by the number of creatures in the area and add the total to the pool, removing monsters when the pool crosses over the hit points of a single monster.

Example: Fifty Skeletons

Let's say you're running a battle with 9th level characters who opened up a huge tomb and unleashed fifty skeletons. We round the hit points of each skeleton up to 15 just to keep the math easier. We could lower it to 10 hit points if we wanted them to drop faster.

Our fighter hacks at the skeletons twice, using power attack. On the first hit, she does 22 damage. That hit hews down one skeleton, and carries 7 damage over in the damage pool. Her next swing hits for 25 damage. This second attack brings the damage pool to 32 – enough to kill two skeletons. We remove the two nearest skeletons, reset the pool to zero, and carry over the remaining 2 damage.

Now the wizard drops a fireball into a horde of the skeletons. The resulting inferno likely kills all of the skeletons in the blast, so we remove them all as their burning bones fly through the air. No math needed – just colorful narrative.

If the wizard instead fires off burning hands for 10 damage against four skeletons, we multiply the damage by the number of monsters hit – a total of 40 damage. We remove two skeletons and carry over the remaining 10 damage to the pool. If that remainder was enough to kill a third skeleton, we kill three and reset the pool once again.

Explain the System to Your Players

When you're running a new system like this one, describe it to your players so they won't be surprised. When you've used it enough, players understand how a damage pool differs from damage done to individual monsters. It often benefits them so players aren't likely to complain.

Why Not Minions?

Some GMs prefer the 4th edition style of "minions" which have only 1 hit point. If a minion is struck with a successful attack or fails a saving throw, it dies. While this shortcut is simple to use, it tends to make monsters too weak. The damage pool solves this issue by giving monsters the same hit points they have as individual monsters but an easier way to track the damage done to the group.

A Tool for Fantastic Storytelling

This damage pool concept goes hand-in-hand with other techniques for running hordes such as managing multiple attacks and multiple saving throws. The damage pool, however, works well on its own to manage tracking damage even when you have lots of monsters on the table.

More Sly Flourish Stuff

This week I posted a couple of YouTube videos on Finding Players for Other RPGs and my prep for Shadowdark Session Zero – The Gloaming.

Last Week's Lazy RPG Talk Show Topics

Each week I record an episode of the Lazy RPG Talk Show (also available as a podcast) in which I talk about all things in tabletop RPGs. Here are last week's topics with timestamped links to the YouTube video:

Patreon Questions and Answers

Also on the Talk Show, I answer questions from Sly Flourish Patreons. Here are last week's questions and answers:

RPG Tips

Each week I think about what I learned in my last RPG session and write them up as D&D tips. Here are this week's tips:

Ask players to describe old memories in impactful situations.
Offer opportunities for characters to set up businesses, trade routes, and other establishments that operate while they're off adventuring.
Aim for four to six players.
Consider what choices you offer in any given scene.
Think about what pitfalls a given scene might have.
Roll up treasure during prep.
Mash together mysteries, dungeon crawls, and big battles with waves of opponents into one big adventure.