CR, Challenge, and Engagement in 5e

I would like to take a moment to discuss a topic I see on the web in varying formats. The question is usually a DM posting:

“My party blows through everything so fast, how do I make my fights more engaging.”

~ Every DM at some point

I know I have experienced this feeling before and I’m so sure it’s a universal quandary, I thought I would elucidate some of my thoughts on the matter.

CR

First, I want to talk about Challenge Rating. It is the metric by which the written rules of 5e measure the difficulty of an encounter. The details of how this system is used are found in the Dungeon Master’s Guide pg 81 – 87, but effective breaks down into a couple of steps.

• Determine the difficulty you want the encounter to be (easy, medium, hard, and deadly).
• For each character, look up the XP threshold for that difficulty (6th level medium: 600, 5th level medium: 500).
• Calculate the party’s XP threshold by adding them all together. You will need this for all encounters for this party. You may as well calculate it for your party now, keep it around and update it when they level.
• Calculate the total monsters XP. This is actual XP you are giving the PCs when they defeat that monster.
• Modify the monster XP total for multiple monsters—a simple multiplication based on that table.
• Compare the modified monster’s XP total to the party’s XP threshold.
• There is more in the document about handling larger parties and creating an adventuring day budget. But the above is all we need to create a single encounter and get a metric of its difficulty.

My friend and author commented below about the Xanathar’s Guide to Everything, Building Encounters section. It is similar to the above (maybe with better math). You can find more about it in the video by Nerdarchy below:

Challenge

To make encounters feel more challenging, you can add environmental hazards. Maybe a movement-altering wind, difficult terrain, or noxious gas. Also, there are some great resources on action-oriented design (check Matt Colville for details). Finally, Mobs in higher numbers are absolutely where the challenge rating multiplier happens, use it. A party is usually only challenged if the enemies meet or exceed the party’s action economy.

All that said, the real challenge of any encounter is built on the feelings of the players. How do they feel about the encounter? Your monsters may be on the ropes, but you can still raise the stakes using narrative and wordplay alone. I argue that the true feeling of the challenge is born, not in monster stat blocks, but in players’ engagement.

Engagement

To really immerse players in a combat scenario requires a couple of things. 

1. First, you need buy-in. The players need to be willing to engage with the combat as though there are real stakes. 
2. Second, You need stakes. the stakes should be high enough that the players are legitimately tense about failing. The stakes should not always be “beat the baddies.”. Sometimes its save the NPC, “prevent the baddy from finishing the ritual,” or “protect the children from the baddy-caused hazard.”. Stakes define why the party fights and are critical for engagement. 
3. Lastly, Narrative is essential to a compelling battle. We all know under the hood combat is a series of “hit, miss, hit, miss, save, damage, win,”. But the narrative of battle is a control lever for tension. How you describe the actions of the monsters or their reactions to damage matters. Describing how the claws of a beast pierce through the PC’s armor, like paper, adds tension.

I like to describe any attack that beats the unarmored AC of a character as a hit. Dealing 0 damage, deflected off the armor. Dinging the armor or loosening the buckles for non-damage combat gives doubly a sense of verisimilitude and drama. “Whoa, it hit my armor, I felt it. The enemy’s aim improves”. 

Also, You can add dramatic narrative by describing failed checks on the part of the adventurers in a believable way. Nobody believes that Robert Dobbs, a longsword wielder since he was a boy, rolled a 1 when attacking that bandit because he forgot how to sword. Instead, he turns to strike the bandit and sees the face of his childhood friend. Driven to stealing during hard times. Challenge the players’ hearts, and you will bind them to amazing storytelling.