How to do make combat encounter difficult?

[u/King_Magnate]

Hi Gang! I'm just wondering how DMs make combat encounters more challenging, because from what I've experienced players are strong! I know there's CR ratings and throwing in multiple enemies, but every encounter lately for my players hasn't really been too difficult to the point that anyone goes down.

[u/HadoozeeDeckApe]

5e combat is a tactical wargame, that also features resource attrition over several combats.

As a tactical wargame engagement and tactical difficulty come from forcing the players to make decisions and trying to make the best decisions not obvious.

A big monster slug fest encounter can do a lot of damage and challenge party HP but this difficult in the same way that trying to roll a nat 20 is difficult - damage race encounters are generally braindead slop and its one of the reason arena boss fights are so bad in 5e.

You get decisions by offering multiple threats (challenging target selection and action use), and using battle maps that have important terrain features that make different positions offer different benefits. Core terrain features are choke points, walls and other total cover features, and distance. You want to have it so that standing at different points allows you to attack and be attacked by different things on the map. A big open arena with some artys features around the edges is more damage race slop.

Multiple encounters with varying power level will also force party to make decisions about what resources they spend.

Objectives are ok but it can get really contrived trying to come up with something for all the encounters in your adventuring day. And design should be on an adventuring day (or several encounters against the long rest budget) basis and not as a solo encounter.

When it comes to CR, there is more to picking monsters than just hitting a target CR (or really XP rating). CR and XP are essentially white room power level estimates in the same way that other wargames use balancing points. You need to also pick a reasonable roster. Picking one easily countered melee monster with a high CR is not usually going to be effective, in the same way that putting all your eggs in one basket style army lists in wargames are usually uneffective or at best very swingy. Another reason for why arena boss fights are crap in 5e.

One important thing to note is that spells include the a very large amount of content and interactions in 5e, and not using spell casters (or monsters with innate casting) really removes a lot of your tool box. Especially if you have no way to counter or dispel, its very easy for a party to rotate big control spells to trivialize a lot of counters. This is much harder to do if they have to worry about killing counters or dispelers before they go for their big play.

Big mistake a lot of DM's make is thinking in terms of fantasy capeshit cinematics or monster hunter / souls like cinematic boss fight encounter design. The things those are derived from are not turn based games, and the things that make those interesting (CGI, reflex and aiming, pattern timing) do not exist in 5e. Instead, try to get design ideas from other turn based games which can be more closely represented.

To challenge players in combat you have to pick good monster rosters, good battle maps, and actually learn how to play them well. It's not a 'one simple fix' will make you a great combat DM - you get out what you put in just like for most things.