Unearthed Arcana Review: Encounter Building

The newest Unearthed Arcana is actually for Dungeon Masters! And it’s a fix for one of the fiddliest systems in the game: encounter building! WOOO! Sound the alarms, or the dubstep or something! I don’t know! This never happens, I’m not sure how to react! Where’s my party horn? I need a hat. And confetti. And another hat! This is a momentous occasion, and must be celebrated as such!

Except…wait. It’s basically just a series of over-done tables? And its attempt at quantifying complications in combat is to…not quantify complications?

Guess I’ll put away my party hat and get out my keyboard. It’s time to go to work.

What’s Actually in the Document?

The document attempts to break down the process of building encounters into 5 easy steps.

  1. Assess Characters
  2. Encounter Size
  3. Determine Numbers/Challenge Ratings
  4. Select Monsters
  5. Add Complications

It should be noted that, although this isn’t explicitly stated within the document, these encounter building guidelines are very much meant to be for Dungeon Masters doing prep-work. This is NOT a document that will see a lot of use at the game table. I’ll get to why that is later. Until then, let’s go over these steps.

1. Assess Characters

The basics of this step include knowing the general power level of your party, how much damage they can do in a single attack, and what their composition is so that you can plan what types or “roles” you need to fill in order to create a challenging encounter.

2. Encounter Size

This is pretty self-explanatory. How many enemies will your party encounter? One big one? A ton of little ones? A team roughly comparable to your own? A duo? A trio? In particular, it dedicates most of its word count to the basics of how legendary monsters can help to improve your combats against a solo opponent, and how you should determine solo enemy CR based on your party size.

3. Determine Numbers/Challenge Rating

Here’s the real meat of the document. It finally breaks down encounter difficulty using CR, rather than experience points, as is presented in the Dungeon Master’s Guide. It then provides four tables, each ranging 5 levels, telling you the ratio of players to enemies for various CRs.

4. Select Monsters

Here, it discusses which monsters you should pick for your encounters, and how certain enemies are balanced in certain ways. It’s essentially a fluffier way of discussing monster roles from 4th edition.

5. Add Complications

Here, it vaguely discusses the advantages of adding different complications to an encounter in order to make things more interesting. Specifically, it discusses Monster Personality, Monster Relationships, Terrain and Traps, and Random Events (environmental effects).

The Good

There’s a lot to like about this document. I like that it’s more than just an encounter-difficulty-by-CR table, which it could have easily been. The discussion of understanding party composition, monster roles, and encounter complications means that newbie GMs who read this are definitively going to start making more interesting encounters for their games.

I also like the ratio breakdown of player:monster. While using XP as your metric on the Dungeon Master’s Guide really does allow for plug-and-play encounter design, the fiddly numbers makes it more difficult than it needs to be. Knowing the exact ratio for a particular CR allows you to understand at a glance the effective power of a single character.

The Less-Than-Good

Could those tables be any more obtuse? I had to re-read step 3 twice to find the text discussing what the ratios actually meant buried inside one of the paragraphs.

In addition, while step 5 shows thought into how interesting events are structured, it doesn’t really include any thought into how to mechanically integrate traps or environmental hazards into your game. It presents the ideas, but doesn’t spend any time fleshing them out, trusting you to do it yourself. And since this is obviously a document for less-than-experienced GMs, that could lead to disaster. An errant lightning strike that deals too much damage, a harsh wind that turns an archer useless, or a trap that entangles and disables a mage can turn a battle from challenging to impossible, so some guidelines would be nice.

And finally, as I stated above, this is a document intended for GM prep. And while that’s all well and good, it is entirely unhelpful when it comes to on-the-fly encounter building, and will see very little use at the game table. For some who like designing encounters ahead-of-time, that’s probably fine. But for someone like me who generally has a few setpiece scenes and then fills in the blanks via improv, I don’t see a whole lot of use for this.

Fixing It

There’s really no way to fix those tables, other than to spell out the ratio. It’s CHARACTERS:MONSTERS. Once you understand that, and understand the method of using them (find Character Level, Find Ratio, Determine CR), they can actually be quite useful.

Traps and Hazards

As far as the traps/environmental hazards, it’s not actually very difficult. I’m going to sound like a broken record again, but let’s once again turn to page 274 of our Dungeon Master’s Guide and our trusty Monster-Statistics-by-CR table! See, the thing is, when it comes to traps and environmental effects, they’re actually just monsters in disguise. How, you ask?

Well, think of it this way. Let’s say you have a climactic battle on a bridge, and you want the enemies (hobgoblins, for example) to set the bridge on fire. The players are going to be fighting the flames as much as they’re fighting the monsters. This effectively makes the fire a participant in the battle. This means that the fire should have statistics appropriate to a monster of its caliber. Assign it a CR, and reference the table for appropriate statistics. Damage per round and Save DC especially should be noted (and keep in mind that something like fire, which has the potential to damage multiple characters per round, should have its damage divided by the number of members in the party).

And the same rules apply to most environmental effects. Lightning bolts during a storm have a save DC and a damage per round. A strong wind probably has a wisdom save to aim appropriately, or an “armor class” that you have to beat in order to stand a chance of hitting an enemy. If the effect has “actions,” then I suggest using a flat initiative roll of 20, just like lair effects on legendary monsters. This keeps things simple and consistent, and easy to manage.

Traps should be handled the same way. The Dungeon Master’s Guide has some basic rules on how traps should work, giving general DCs and damages based on level and “difficulty” of the trap. MY suggestion is, again, to treat the trap like a monster. Assign it a CR, include it in the lineup of your encounter, and use as appropriate.

The problem with traps when compared to environmental effects, however, is that traps are usually one-off attacks or effects. They usually don’t persist. This isn’t always the case (a spinning blade that damages anyone who gets too close, for example, or a statue that breaths fire whenever someone’s near), but most standard traps function this way. An arrow trap or a land mine work exactly once.

If your trap functions this way, firing off like a bottle rocket and becoming inert, then I suggest taking the damage per round of the appropriate CR and multiplying it by 2. This is even, to a degree, backed up by the standard trap rules. It suggests from 1st-4th level that a “dangerous” trap (the middle tier) should deal 2d10, or 11 damage. This is roughly consistent with a creature of CR ¼, which deals 4-5 damage. Double that and you get 8-10. And if we check our ratio table, we see that CR ¼ is 1:1 with a character of 1st level. Checking the numbers for the other levels and suggested damages reveals similarly appropriate numbers.

If your trap, however, has ongoing effects, then I would suggest sticking to the base damage per round. A pit trap, for example, might only deal the damage once, but requires a character to make a Strength (Athletics) check to climb out, cutting them out of the battle for a number of rounds. If it’s filled with acid, then it’s also doing damage every round.

Treating traps and environmental effects as monsters in this way does two things to help Dungeon Masters. First if all, it gives you a consistent measure by which you can gauge the challenge of a particular obstacle, allowing you to appropriately challenge players with non-combat encounters. Similarly, this method establishes how much XP a particular trap or environmental effect should grant. A CR 4 poison arrow trap, for example, will grant 1,100 XP when survived or disabled.

Usability at the Table

This is an area that’s a bit more difficult to fix. In general, I find that Sly Flourish’s Encounter Building Rules are the most table-friendly. However, they build toward a “hard” fight, rather than a “medium” fight. And when I try to come up with an easy equation for medium difficulty, it just doesn’t come up. The math never quite fits. So if you really want something that will be useful at your table, then use Sly Flourish’s rules, adjusted to make an encounter easier or more difficult as necessary. If you’re too lazy to click over to his page, here’s the basics.



This was a pretty good document, all told. Despite how little use I personally will get out of this Unearthed Arcana, I think that it will be a valuable tool for prep-heavy GMs. The thought behind it is definitely in the right place, and its promotion of complications in order to create interesting encounters is admirable. Overall, I say definitely give this one a read—even as an experienced GM. You might just get something out of it.


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One thought on “Unearthed Arcana Review: Encounter Building

Add yours

  1. Thanks, I too had a somewhat difficult time keeping the various aspects of the tables straight. Also, cool idea for giving environmental effects, etc a CR. My utter lack of DM experience thanks you.


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