Tips for encounter building?

Does anyone have some good, practical general advice for making good encounters? I’m finding the system of challenge ratings and scaling encounters really difficult to use, both in how CR is calculated for individual creatures and how creatures from the list for an encounter are chosen to be spawned. Eg CR doesn’t take creatures’ equipment into account, even though base AC is a factor and you can give them armour that adds +8 AC. And then it’s hard to figure out how it selects creatures to spawn, and it seems to have quite low granularity when I change the difficulty, like an easy encounter will spawn two low-cr creatures but a medium one will spawn like five low-cr and two higher-cr creatures, and there’s no middle ground.

Fortunately I’m making a small-scale single player module where I know roughly what level the PC will be at a given point, not a persistent world or anything, so I don’t need the encounters to be able to perfectly scale across a big range of levels. I’m still having a lot of trouble though.

If you have lots of experience building encounters could you share any tips?

The first thing to keep in mind here, which you seem to be catching on to, is that the formula used to calculate a creature’s default CR is quite wonky and tends to produce wildly inaccurate results that very frequently bear no relation to how actually challenging the creature is. Thus, if you are making use of CRs for anything important in your module, it is generally a good idea to manually set creatures’ CR to something more appropriate than the default.

In addition to assigning accurate CRs, encounters also need a wide range of creatures with lots of different CRs in order to pick out an appropriate set and scale reasonably. To take an extreme example to make the point, if the only creatures an encounter could pick were a CR 40 and and a CR 1 creature, it would have a hard time coming up with an appropriate spawn for a Lvl 10 adventurer. What you would want (in an encounter aimed at Lvl 10 players) is a variety of creatures with CRs spanning something like 8-12.

Assuming CRs have been set to something reasonably close to the creature’s actual challenge, and that there is a wide range of CRs among the available creatures, the encounter system can actually do a pretty good job of scaling encounters. Unfortunately those preconditions are not always that easy to meet.

For your purposes, it is not clear that you actually need to use the encounter system, since the point of it is to scale encounters to match the number (in multi-player) and level of PCs. For a single player module linear enough that the PC’s level at any given point is predictable, using non-scaling encounters of creatures either pre-placed or spawned by a simple custom script could work as well or better.

The CR actually does take items into account, but like most everything else it does so in a wonky way, so typically you need to give creatures very powerful magical items to notice much difference. Among other oddities, a single item with lots of magical properties will tend to raise a creature’s default CR much more than the same properties spread out among multiple items. However, I think the encounters only take the number and level of PCs into account, which could be an important consideration. For example, in a high magic module where PCs have access to very powerful gear, the encounters spawned will tend to be too weak.

Ultimately, to have well desgined encounters, you need to do a lot of playtesting, ideally with a wide variety of different builds, to find out in actual practice how hard they are, and tweak the number and stats of creatures spawned to adjust the level of challenge to what you want.


It may sound a little strange, but common sense goes a long way in designing encounters. Lvl 1 PC = goblins, Lvl 3-4 = orcs, lvl 6-7 = trolls, etc. Companions for SP modules will make a significant difference to combat difficulty, though, for example being able to take a cleric into an undead encounter and such.

On a practical level, if you’re using the toolset encounter trigger system, then you in fact have a lot of control over the outcome by setting the min/max number of creatures and using the “unique” checkbox in the creature list. It works best when you have a good idea of the mix (say 4-6 creatures, 1 stronger one) for each particular encounter. Trying to use much broader encounter triggers for many different situations ends up being too random.

If you really want to get down in the weeds on NWN CR calculations and encounters, you can always check out Lazybones’ classic DM guide, which while intended for multiplayer has a section on encounter calculations.

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@rogueknight333 and @Carlo

Thanks so much for your replies, that’s really helpful. I think perhaps the fact that my module is, as you say, linear enough that pc level for a given encounter is predictable (plus number of PCs is absolutely predictable as it’s sp only) actually means the encounter system is not just less effective but actively unhelpful, in these circumstances. I will look at using custom scripts and triggers to spawn enemies instead.

here’s a guide that used to be popular. it covers the basics.

Building_Challenging_Encounters2.pdf (967.5 KB)

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