by Mike Shea on 12 September 2016
Note: This article is a rewrite of the original from March 2015. Recently Wizards of the Coast released a new Unearthed Arcana encounter building rules which gives us a new way to build encounters on top of the rules in the Dungeon Master's Guide. Consider these guidelines a third alternative for fast, simple, and loose encounter building.
The following guidelines aim to help dungeon masters running the 5th edition of Dungeons & Dragons build combat encounters quickly and easily. This article begins with a set of quick encounter building guidelines and then get into the design considerations later in this article.
These guidelines are intended to give us a rough idea what number and challenge rating of monster equates to a "hard" encounter so we can tune our own battles from that baseline depending on the story and our goals. These guidelines, like the underlying challenge rating of monsters, is not an exact science and will not build perfectly balanced encounters. Nor will any other system. Instead, it gives us an easy-to-remember guideline for determining the rough balance of monsters to characters for challenging encounters.
You can download a one-page formatted PDF of these guidelines suitable for printing.
The following is a more detailed look at the guidelines above. Note, these are intended to help you understand what a "hard" encounter looks like so you have the freedom to tune the battle to make it easier or harder depending on the story and your goals for the encounter.
1. Start with the story. What type of encounter makes sense for the current location and direction of this story? You might know this ahead of time or might want to build a quick encounter right at the table. When designing an encounter, start with the story first and the mechanics second.
2. Choose appropriate monsters. Use the monsters by challenge rating index or the excellent Monsters by Environment list in appendix B of the Dungeon Master's Guide to help you choose the right monsters for the encounter you want to build. Aim for creatures with a challenge rating roughly equivalent to 3/4 the level of the characters or less. If you're aiming to have them fight a single monster, the challenge rating should be at the character's level or up to two ratings higher.
3. Determine the number of monsters. Choose a number of monsters based on the monsters' challenge rating compared to the characters' level. For monsters with a challenge rating of 1/4 the character's level, use two monsters per character. For monsters with a challenge rating of 1/3 the character's level, use one monster per character. For monsters with a challenge rating of 3/4 the character's level, use one monster per two characters. For monsters with a challenge rating equal to or above the character's level, use one monster per four characters.
Here's a quick lookup table. Note that this table better follows the encounter guidance in the Dungeon Master's Guide than the simple equations.
|Character level||CR for two monsters per character||CR for one monster per character||CR for one monster per two characters||CR for one monster per four characters|
4. Adjust difficulty. These guidelines aim for a "hard" encounter as described on page 82 of the Dungeon Master's Guide. Increase or decrease the difficulty by adding or subtracting monsters, choosing monsters with higher or lower challenge ratings, or by increasing or decreasing the monsters' hit points.
5. Evaluate the action economy. Compare the number of monsters to the number of characters. Too many creatures on one side or the other will have a big effect on the difficulty. Big monsters that fight by themselves are much easier to defeat than a somewhat big monsters with a couple of lackeys to keep the wizards busy. In general, when facing a large "boss" monster, add one or two monsters of a CR roughly 1/4 to 1/3 the character's level for each character above four.
The rest of this article discusses the design philosophy behind these guidelines. You need not read further unless you wish to understand how and why these guidelines were put in place.
The guidelines above let you mix and match a bunch of different monsters in a single battle by matching monsters with different challenge ratings with the level of the characters. For example, if you have a group of five level 7 characters, you can build an encounter with one challenge 5 troll (the equivalant of two level 7 characters), two challenge 2 ogres (the equivalant of two additional level 7 characters) and two challenge 1 bugbears (the equivalant of the one remaining level 7 character).
The math isn't perfect since 1/3 of level 7 and 1/4 of level 7 both round out to challenge 2. Theoretically you could have five ogres and a troll instead of two ogres, a troll, and two bugbears. That's certainly a harder battle but it still falls within the guidelines.
The challenge of any encounter in 5th Edition Dungeons & Dragons cannot be easily measured or quantified. There are too many variables to know how any battle is really going to go. Some of these include variance between monsters at the same challenge rating, the class mixture of characters, the particular spells a character group has access to, who wins initiative, circumstantial or environmental considerations, and the skills and proficiency of the players. The Dungeon Bastard reminds us that whether a group is fully rested or worn down will have a huge effect on how easily they can overcome the next battle.
Thus, all systems to determine the difficulty of an encounter in 5e will lack precision.
Due to the complexity of the encounter building rules in the D&D 5e Dungeon Master's Guide and the lack of precision in any encounter building system, we aim for a faster system that gives dungeon masters loose guidelines to balance encounters while acknowledging that the actual difficulty will still vary.
The encounter building tables in the Dungeon Master's Guide or the DM Basic Rules offer four levels of difficulty: easy, medium, hard, and deadly. As a rule of thumb, however, we really only need to worry about the "hard" battle. If we use fewer or lower challenge monsters than the "hard" budget allows, the battle is easier. If we use more or bigger monsters, the battle will be harder. This gives us a single baseline we use to balance each encounter instead of worrying where it fits within a range of four imprecise difficulties.
We calculated these guidelines using the traditional encounter building rules aimed at a "hard" encounter and using the multiplier for the number of monsters assuming that the number of monsters will be roughly comparable to the number of characters. We make the assumption that most battles will have a roughly equal number of monsters to characters. Adjusting the difficulty from this baseline is easily done by removing monsters, choosing lower challenge monsters, or increasing or decreasing hit points.
We intend for these encounter building guidelines to be easy enough to keep in our head and usable right at the table when we want to build an encounter right now. We intend for these rules to aid in improvisational DMing with very little, if any, preparation required before the game is run.
There's a good reason the Dungeon Master's Guide has two tables we must cross reference to put together an encounter. Regardless of the individual power of a monster, the difficulty goes up every time we add another combatant to the battle field. Regardless of how hard they swing a sword, two knights get twice as many actions as one.
We call this the action economy. The more total actions on one side of a battle, the stronger that side is. The multiplier in the standard encounter building guidelines intends to account for this. If there are three to six monsters, they are significantly more effective than if there is only one. Thus we have a 2x multiplier on their experience point budget when we include them into an encounter. This increase in the action economy is why the rules for encounter building are so complicated. As Benjamin Reinheart often points out, the overall threat in combat increases at a geometric rate as you add more combatants to a fight.
For this reason, you likely want to have no fewer than one monster for the first four characters plus one additional monster for each character above four. Even an ancient red dragon is going to have trouble handling six high level characters and all of the things they can do in a round.
The intent of these guidelines isn't to ensure that every encounter our characters face is balanced. There should be many times our characters face small groups of easily defeated monsters and a few occasions where they might run into a foe they simply cannot defeat with straight-on combat. Instead, these guidelines are intended to give us a gauge to help us understand how any given battle might go. If we're way above the baseline, we know things are going to be rough and can help our players see that. If we're going way below, we know it will probably be an easy fight. Varying difficulty is a good way to ensure the story and the game feel fresh.
As we begin to understand our group's actual power, we can alter these guidelines to face them and D&D 5e's speed of combat makes it easy to do so. If a group of experienced players is running a strong group of well-coordinated and well-built characters, we can increase the challenge dramatically by increasing the challenge rating of the monsters we choose, increasing the number of monsters in the battle, increasing the hit points of those monsters, or increasing their damage. We can also go in the opposite direction with groups who aren't as experienced or well-coordinated. Fewer monsters, monsters of a lower challenge rating, or both will make battles easier for less optimized groups of players.
Again, these are loose guidelines meant to give us a starting point. As DMs, we are free to tweak these guidelines depending on our goals and the actual results we see at the table.
As Chris Sims stated above, the higher level the characters, the more the standard encounter building rules break down. Strong groups of characters played by experienced players can fight deadly battles far outside of the baseline for a "hard" encounter and still win. Other less experienced groups will have a harder time with such battles.
As DMs, we can start by using these guidelines and then tweak them as we need once we know more about the actual strength of our groups.
We built these encounter building guidelines to make your life easier when putting together a battle. Keep these numbers in your head: For monsters with a challenge rating of 1/4 the character's level, use two monsters per character. For monsters with a challenge rating of 1/3 the character's level, use one monster per character. For monsters with a challenge rating of 3/4 the character's level, use one monster per two characters. For monsters with a challenge rating equal to or above the character's level, use one monster per four characters. With that in your head you can quickly build a roughly balanced encounter for a challenging fight. Tweak to suit these guidelines to match the skills of your players and the power of your characters and focus your attention on the grand story of the game you share together.
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