D&D 5E Making Challenging Combats?

[Retreater]

Coming back to 5e after some time in other systems (WFRP, OSE, PF2), it's hitting me that I'm having some trouble building challenging fights. I have five 6th-level characters (paladin, ranger, cleric, wizard, and monk), and they are easily handling battles that are considered "Deadly" by the encounter building guidelines (12th and 13th level fights).
Is there a rule of thumb that you use to present a decent challenge for a standard fight? I'm certainly not looking to TPK the party, but just enough where they have to use some tactics and sweat a little during a battle instead of the group being basically unscathed with most of their resources remaining.
And yeah, I know I can add complications to the fights (monsters who can't be grappled, battles underwater, combats that require navigating creative obstacles and traps), but this design would be exhausting for me to prepare for every fight and would likely get frustrating for the group.
What do you do? Like, do you stage 16th level challenges for such a party?

 

[Reynard]

Are you using too few enemies? 5E combat difficulty is easily impacted by enemy action economy. Increase the number of enemies and ignore the weird XP multiplier for doing so if you are using the CR calculator.

 

[Retreater]

Are you using too few enemies? 5E combat difficulty is easily impacted by enemy action economy. Increase the number of enemies and ignore the weird XP multiplier for doing so if you are using the CR calculator.

Four enemies - against five characters. Should I strive to outnumber the party?

 

[prabe]

I'd at least go even numbers, maybe even numbers plus a leader-type (not necessarily a "boss" if that's a distinction that makes sense).

I'm going to remind you of two things that might have fallen out of your thinking while you were running other games: First, by CR, fights don't start getting really difficult until "deadly"; second, WotC's monsters tend to be a bit undertuned, compared to like the CR calculator. The upshots are (A) what you're experiencing, where the fights aren't as challenging as the words say they should be, is typical and maybe intentional; and (B) if you use third-party critters, you need to be a little more careful, at least at first.

 

[el-remmen]

If coming up with obstacles and unique environments would be "exhausting for [you] to prepare for every fight and would likely get frustrating for the group," then my advice of customizing all/most of the monsters probably also won't work for you.

I usually use this site to create custom stat blocks (stealing existing abilities from other monsters - or just making up my own and saving them for future use).

 

[Reynard]

Four enemies - against five characters. Should I strive to outnumber the party?

Absolutlely At least equal their numbers but I tend to make it more than the PCs (sometimes twice as many but not usually) because it forces the PCs to make choices about who to protect and how, or whether to use AoEs that might catch allies, etc...

 

[LordEntrails]

First, don't use the encounter building guidelines from the DMG.
Second, I almost always outnumber the PCs. 2:1 is common, but 4:1 is not unusual (but you need to be using a good VTT with automation to keep this from having combats turn into slogs).
Third, remember, NPC CR is NOT equivalent to PC level. Not even cclose.

 

[Stormonu]

Four enemies - against five characters. Should I strive to outnumber the party?

Generally yes - at least, the monsters should be getting more total actions than the party. This includes Legendary actions and the like.

Also, the system expects you to be running the "5-8" encounters a day, so the fewer you are using before the party stops and rests to recover their abilities, the easier an individual combat will seem. You'll only start to see the player's confidence fray the more encounters are stringed together if you go by-the-book CR. I think WotC went (way) on the lighter side to not frustrate casual players, though they tend to write tougher "boss" encounters in their adventures. Unfortunately, unless the DM is willing to amp up the danger, experienced and hard-core players tend to see the CR system as "easy mode".

When I'm devising my own encounters for CR, I always reach for Deadly+, maxxing out the encounter XP budget WITHOUT using the multipliers for multiple enemies, and going with PC numbers +1 to 2x PC numbers - if I want a challenging fight. I find the PCs in one of my games can handle about three such encounters before having to taking a long rest, while another group I run will have to huddle up and tend to unconscious members after one such encounter.

In the end, you have to know your players and what they can handle. Experienced, tight groups that work well as a team can handle a lot tougher than casual players who barely know what their PCs are capable of, and there's a whole lot of room in-between.

 

[Quickleaf]

Coming back to 5e after some time in other systems (WFRP, OSE, PF2), it's hitting me that I'm having some trouble building challenging fights. I have five 6th-level characters (paladin, ranger, cleric, wizard, and monk), and they are easily handling battles that are considered "Deadly" by the encounter building guidelines (12th and 13th level fights).
Is there a rule of thumb that you use to present a decent challenge for a standard fight? I'm certainly not looking to TPK the party, but just enough where they have to use some tactics and sweat a little during a battle instead of the group being basically unscathed with most of their resources remaining.
And yeah, I know I can add complications to the fights (monsters who can't be grappled, battles underwater, combats that require navigating creative obstacles and traps), but this design would be exhausting for me to prepare for every fight and would likely get frustrating for the group.
What do you do? Like, do you stage 16th level challenges for such a party?

Hi Retreater, yeah I do have my own rules-of-thumb...

First, "deadly" does not mean what you think it means, especially if the party is not having 6-8 encounters per adventuring day (IME most of us don't have that many). Don't be afraid to use Daily Adventuring XP Budget as a guideline or even just your "DM feels." I've routinely seen PCs hit above what the rules would have you believe is their "weight class", such as four 10th levels taking on a CR 16 star spawn larva mage with Lair Actions and a magic item. And I saw that same 10th level party – after being severely taxed – flee a goblin ambush.

Second, I make sure that I'm playing my monsters effectively. Sometimes this means dissecting a stat block before running, and noting down the tactics of maximum effect for the monster. Other times it means staging the scene to facilitate that monster's unique kind of ambush. And other times it means pairing the monster with a suitable terrain hazard/trap or complication. Even just mentally noting "these ghouls ALWAYS attack dying characters and attempt to drag them away to feast on them" or "a shallow layer of water causes anyone knocked unconscious to begin drowning" can add a lot of peril to a scene.

Third, I include ~1 complication, twist, or development per tier of play in most of my serious combats. For a small or newbie group I'll lower this total by 1, while for a large or highly experienced group I'll increase it by 1. So say you have a party of 4 or 5 PCs of 13th level – I'd aim to include ~3 complications, twists, or developments in most of the combats you want to be challenging.

EDIT: I'll address your concern about this being exhausting or un-fun. Obviously, you don't want to use this approach 100% of the time. Variety is the spice of life. Sometimes a lone kobold is exactly what they need to encounter. However, I adopted this rule something like 66-75% of the time, and it really increased player enjoyment and engagement during combat. At least for my group. YMMV.

I can run through an example of this latter point if you have a specific encounter on your mind, maybe one you ran and wish were more challenging, or one you're planning for an upcoming session?

EDIT EDIT: Ah, found my old 10 Dials of Combat Difficulty...

Spoiler

1. Don't let the players always be in control over when they rest, particularly when they get a long rest. For example, if they're on a time sensitive mission, taking even a single short rest before the mission is over could spell disaster.

2. If the party does take a long rest after beginning an incursion on a monster lair/dungeon, have the inhabitants spend those 8 hours bolstering defenses and making appropriate preparations.

3. Define party goals in combat besides "kill all monsters" which offer a different way to use resources/actions. For example, defend an emissary from assassins. The great thing about this approach is that it immerses the players in the game and makes victory independent from hit points.

4. Use tactics suiting the monster types, their Intelligence, and any recon they have on the party. For example, goblins are well known for retreating out of line-of-sight into an area where a lot more goblins lurk with readied attacks...potentially killing a foolhardy PC in pursuit. Whereas cunning NPC mercenaries might use the player's own tactics against them. Keith Ammonn's The Monsters Know is a good starting point.

5. Attack unconscious PCs when it makes sense for the monster in question. For example, an intelligent gladiator who realizes the party has access to healing magic...when he KO's a PC with one attack, he'll use another of his Extra Attacks to stab the PC while they're down, causing 2 failed death saves, and upping the pressure on the PCs to heal that PC immediately.

6. Create scenarios where the PCs may end up out of reach of buffing/healing spells. For example, a chasm with enemy guards watching a wall on the far side who can be easily assassinated by the rogue, but doing so puts him out of range of the cleric.

7. Make the environment favor the monsters. For example, salamanders (immune to fire & able to "swim" in lava) near streams of lava emanating intense heat. Alternately, you can come up with Lair Actions shared by an entire tribe of monsters.

8. Make the environment dangerous. Opportunities to fall seem to be the #1 killer in my games. Kobolds don't stick around to fight unless they have traps. When fighting in a mine, spells like thunderwave or shatter or booming blade might run the risk of triggering a collapse.

9. Increase the number of lower CR enemies, but introduce them in waves. However, be prepared with a way to quickly & clearly track their hit points/conditions. If there are truly a lot, consider using the Handling Mobs rules in the DMG.

10. Don't be afraid to use monsters of significantly higher CR if it makes sense for your story (and you're foreshadowing the monsters). I had four 6th-level PCs (all were fresh) just barely take down a CR 12 titanoboa (from Kobold Press' Tome of Beasts) without any casualties, but they came very close.

 

[iserith]

Something as simple as difficult terrain, cover, elevations, and illumination can have major impacts on the difficulty of a challenge. If you're not including those sorts of things, you are essentially making a white room where the PCs can always easily get to the monsters and execute their Plan A tactics. Make them work for that or have to switch to another plan to be effective. They can also use these elements to their own advantage once they figure out how. (But then so can the enemies.) Check to see what environmental effects might directly benefit the monsters. Add them. See what happens.

Further, if you are not running several fights per adventuring day, the PCs will be well-resourced to handle anything fairly easily. So make sure you're only rarely doing adventuring days with very few encounters. Attrition increases difficulty without necessarily doing anything to the monsters or environment itself.