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Balancing D&D Combat for One-on-One Play

by Mike on 23 December 2019

The D&D Essentials Kit includes the first-ever WOTC-published rules for running D&D with just one player and one DM. This is a whole new style of playing D&D, although some, such as the fine folks behind D&D Duet, have been playing this way for a while and I imagine other groups have played this way for years. Like running combat without a map or minis, some folks think it is completely impossible while others have done it for years without issue.

Being able to play D&D one-on-one has tremendous advantages. It's much easier to find a group when you only need one other player. Games can go quicker and the story can go further in each session with a single player than with a larger group. The story of the game can focus on that one particular character. The story, maybe the whole world itself, can be built around this single main character. The list of advantages goes on and on. With the right tools and principals in mind for running one-on-one D&D, we might even run a single character through a published campaign adventure such as Curse of Strahd, Tomb of Annihilation, or Tyranny of Dragons.

Most of the steps we use to prepare and run our D&D games changes little when we run for a single player. We can still use all the steps from Return of the Lazy Dungeon Master if we choose. The first step, reviewing the characters, becomes much easier and can also have a greater impact on the remaining seven steps. Running the adventure and the story can work just as well with one character (and a sidekick—more on this soon) as it can for four.

One area of D&D, however, requires careful tuning when we run for fewer than four characters—combat.

Combat encounters and monster design in the 5th edition of D&D generally expects four characters. Beyond their raw capabilities, there's a synergy between four characters that one character alone doesn't possess. Simply removing monsters from a combat encounter isn't enough to ensure a battle will run smoothly in a one-on-one D&D game. We DMs have to keep some concepts continually in mind to ensure our one-on-one D&D game plays smoothly.

The goal of this article is to give you the tools to run any D&D adventure, including the WOTC-published D&D hardback adventures, with just one DM and one player.

The D&D Essentials Kit includes a major aid for running one-on-one D&D—sidekicks. These lower-powered and mechanically simple NPCs are intended to work side-by-side with the main character in a one-on-one game. Sidekicks help bring some of the synergy back when running with only one player but it's still a far cry from four full characters.

A Quick Checklist for Running One-on-One Combat in D&D

Use the following guidelines to help you tune combat encounters when running a game for a single character and a sidekick. This articles goes into each of these guidelines further on.

Reduce the number of monsters the character faces. Be careful when including more monsters than the number of characters including sidekicks.
Reduce the hit points of monsters as needed.
Reduce the number of attacks and damage of monsters as needed.
Remove legendary actions, lair actions, and legendary resistance from legendary monsters. Tune them to suit the battle.
Give the character relics, scrolls, potions, and magic items to off-set their gaps.
Be wary of monster spells or effects that can, with a single stroke, remove the character from combat.
Run larger battles off-screen. Describe groups of allied NPCs facing off against large groups of monsters.

On Sidekicks

Sidekicks, first released in this Unearthed Arcana Sidekick document and then later published in the D&D Essentials Kit, are a big boon for running one-on-one D&D games. Sidekicks help fill in the gaps a single character will have when facing the world in a D&D game. A fighter character, for example, can have a healer sidekick who keeps them healthy. A wizard character can have a defender sidekick who protects the wizard from powerful foes. Sidekicks have skills, abilities, and spells that aid the character as they face challenges ahead. During the game, sidekicks can regularly use the "help" action to give the character advantage on most checks when needed.

The D&D Essentials adventure, Dragon of Icespire Peak, includes rules to level sidekicks up to 6th level while the three supplementary adventures available on D&D Beyond offer rules to take sidekicks up to 12th level. If this isn't enough, or you don't have access to these adventures, you can use the Unearthed Arcana Sidekick guidelines to create sidekicks up to 20th level starting with a baseline NPC stat block. One advantage of the UA sidekick rules is that you can apply them to any stat block in the Monster Manual. Thus, a character can have a town guard, a pet spider, or a flying snake that gains levels as they do.

Tuning Combat Encounters

With a character and sidekick prepared, it's up to us DMs to tune combat encounters to support one-on-one play. It isn't enough to simply reduce the number of monsters, although that's a big part of the equation. We have to remember the lost synergy a single character has when compared to a party of four.

In previous articles we've talked about how to increase the challenge of monsters in D&D combat. This mostly fell into three simple steps: increase monsters, increase their hit points, and increase their damage. These are three big dials we DMs control that can dramatically change the difficulty of a combat encounter. Likewise, when we're running one-on-one D&D games, we can turn these dials the other way, reducing the number of monsters, reducing their hit points, and reducing their damage. That's most of what we need to do when running combat one-on-one in D&D.

Selecting the Number of Monsters

The number one variable in combat difficulty is the number of monsters the characters face. In a one-on-one game, we should pay careful attention to how many monsters our character will face, particularly when there are potentially more monsters than characters. We can use our encounter building guidelines to get a rough gauge for the appropriate challenge rating for a character to face at a given level. We can use the following rough guide to gauge whether a fight might be deadly. In general, a character should rarely face more than the following:

For a 1st level character

One creature of challenge 1/4 or less

For a 2nd to 4th level character

One creature of a CR 1/4 of the characters level.
Two creatures of a CR 1/10th of the characters level.

For a 5th to 20th level character.

One creature of a CR 1/2 of the characters level.
Two creatures of a CR 1/4 of the characters level.
Four creatures of a CR 1/10th of the characters level.

Generally speaking, except in rare circumstances based on the story, should the character face more than four opponents. Four opponents puts a single character at a great disadvantage, particularly when they don't have the synergy of the rest of the party.

Note that, in general, we'll ignore the sidekick when selecting the number of monsters. Sidekicks, while helpful, aren't as powerful as characters.

For more info on these ideas, Jonathan and Beth at D&D Duets have an excellent article on scaling D&D encounters for one-on-one play.

Reducing Hit Points and Damage

Two other dials help us control the difficulty of combat in D&D: hit points and damage output. We can increase or decrease hit points as needed to increase or decrease how long a monster takes to defeat within the range of a monster's listed hit dice range. Typically, when facing more characters, we might increase a monster's hit points to keep it around longer. When running D&D for only one character, however, we likely want to reduce a monster's hit points as needed. You'll need to play this by ear as you run combat. If things are taking too long, consider reducing the monster's hit points on the fly. If things are going smoothly, the monster's average hit points might be fine.

Likewise, a creature's damage, including extra attacks, are often intended for use when facing four or more characters. When we're running only one character, we may want to either reduce the damage of an attack or reduce the number of attacks a monster can make.

Let's look at ogres as an example. In the D&D adventure Dragon of Icespire Peak, the characters may face off against two ogres and a number of orcs in the Shrine of Savras. When running for a single character (as I did with Newbie DM) we can start by reducing the number of ogres down to one. One ogre is a significant challenge for a 3rd level character, even with a sidekick, and it's very dangerous when you throw one or two orcs in as well.

A standard ogre has 59 hit points. A really tough ogre could have as many as 91 hit points. A weaker one could have as few as 28. We'll stick to 30 hit points for our one-on-one ogre. An average ogre hits for 13 with a greatclub. A powerful ogre may hit for as much as 20. A weaker ogre may hit for as little as 6. We'll call it 8. If we want to roll dice for damage, we'll convert this to 1d6 + 5. This ogre is still dangerous for a single 3rd level character but it won't knock them out with two hits.

If we're looking at orcs, we might switch their greataxes out for regular battle axes, reducing their damage from 9 to 7 or even handaxes for 6.

We don't have to plan this out ahead of time. We can make these changes as they're needed during the game itself. Pay no attention to that man behind the curtain.

Keeping our hand on the dials for the number of monsters, their hit points, and the damage they put out can help us ensure we're providing the right challenge for the character in our one-on-one D&D game.

Tuning Legendary Monsters

Legendary monsters are built specifically to handle battles against four or more characters. They accomplish this (at varying degrees of success) by including legendary actions, legendary resistances, and lair actions.

Tuning a legendary monster for a battle against a single character and a companion character is mostly a matter of rolling back these advantages. When we're running a legendary monster against a single character and their companion, we can remove the monster's legendary actions, legendary resistances, and lair actions. This brings the monster's damage output and number of actions back in relative balance with a single character and a companion.

Depending on how challenging the fight is, we might have to further modify the legendary monster to bring it in line by the character. We might, for example, need to reduce its hit points to put it more in line with the damage output of the character and their companion. We might need to reduce its damage as well, even after removing legendary actions.

Handling Save-Or-Suck Effects

Save or suck effects are effects that severely debilitate or remove combatants from combat. Spells such as dominate monster, sleep, or hypnotic pattern all count as save-or-suck abilities (some, like sleep, don't even give you a save). Monster effects like a banshee's wail, a vampire's charm, or about half of a beholder's eye rays all count as "save-or-suck" abilities.

These abilities may remove the threat of a single character in a group when a group of characters face a monster but in a one-on-one game, they may completely remove the threat of the entire party all at once.

We have to be particularly careful running monsters who have save-or-suck abilities against the characters in a one-on-one game. We can simply remove these abilities, focusing on actions that inflict damage or create less debilitating effects. We might slightly modify these abilities to account for their potential danger. We can, for example, remove debilitating effects after a single round instead of requiring a saving throw. Above all we need to be aware of the problem before it becomes one.

Such effects may steer the story in an interesting direction, however. A character charmed by a vampire might take the story in a totally different direction. This shift in the story may make for great entertainment but it could ruin a game if a player's solo character gets killed by a bad save against a single beholder eye ray.

Keep an eye out for save-or-suck effects and adjudicate them understanding that they were likely intended for a party of four, not a party of one.

Adding Relics, Scrolls, and Potions

A single character in a D&D game is likely to have major mechanical deficiencies when compared to a full group. Fighters, for example, may not have any good way to handle a larger number of smaller monsters. The companion character is intended to off-set these deficiencies but that only goes so far. We may need other ways to shore up these deficiencies.

Healing is an obvious potential gap. If, for some reason, neither the character nor their companion have a magical way to heal; we'll want to add in a good number of healing potions and other potential magic items to offset this.

Area-of-effect spells may be a problem as well. A single fighter and a cleric might be good facing a smaller number of foes but fireball might be a big help that they're not going to ever get. A necklace of fireballs is a great magic item for a fighter to help offset their lack of area-of-effect spells.

We can drop in lots of relics into our games to give more utility to the character and their companion. We can choose some of these randomly or we can select a few that we think help off-set the mechanical gaps the character may have when facing a world that expects a mix of four such characters.

Handling Big Battles Off-Screen

Earlier we talked about running a single character through a big campaign adventure like Tyranny of Dragons. What would it be like for a single character and a sidekick to face Tiamat? First off, we'll remove Tiamat's legendary actions and legendary resistances. We'll move her breath weapon from a legendary action to a normal action. It wouldn't make sense that she can't breathe.

We might give our characters some handy ways to deal with those breath weapons through various potions of resistance or other relics that might help offset her devastating power.

We can probably tweak her stat block in other ways, selectively forgetting about her regeneration and divine word ability. She still has a boatload of hit points and a high AC.

When we have a foe like this, we might consider running some of the battle off-screen. Perhaps the alliance of metallic dragons fighting against Tiamat has already faced her, cutting down her hit points and maybe even disabling a couple of her heads before the character gets involved. Perhaps a group of allied archmages has blasted the queen of dragons, disrupting her regenerating before being incinerated by her dragon's breath, which has yet to recharge.

When we see the story heading towards an area where a single character and sidekick simply can't stand up to a larger foe or force, we can move some of the situation off-screen. If the characters, for example, find themselves about to face forty orcs, we might have a force of allies take on the bulk of these orcs while our hero and their sidekick face the orc leader and her two henchmen. This gives us the feeling of the larger battle without worrying about our character being overwhelmed.

Expanding the World of D&D

Being able to run D&D with just a single player and a single DM dramatically expands our ability to play D&D. It brings D&D to entire groups of people who would otherwise not be able to get four to six of their friends together at any given time. Being able to run D&D one-on-one while still running the hardcover D&D adventures means we can share epic tales of high adventure in which heroes face tremendous world-ending foes. With a handful of simple tricks to tune such adventures we can share tales of high adventure with just a single DM and a single player.

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