Optional Mechanic: One-on-One Combat Rules
These mechanics are meant to make the combat between two creatures, often a player and a Narrator-controlled adversary, feel more like a true one-on-one encounter by zooming in and giving a bit more detail to the attacks and the actions one can take. With that in mind, the Narrator should reserve these rules as a way to highlight specific events or moments within the story.
Due to the way these mechanics are meant to work, they would not translate well into normal combat where the party takes on several enemies at once. To prevent any confusion, the Narrator can simply say that any interference from those not engaged in the one-on-one encounter results in it shifting to normal combat rules.
The Narrator can also institute other rules for one-on-one combat or duels that give it more depth or meaning to their game world, such as:
- Penalties or a forfeit if another creature tries to interfere.
- Giving those attacking from outside advantage on their attacks, as the participants of the duel are completely focused on one another.
- Calling for a Sleight of Hand check from spectators to cast or otherwise interfere without being noticed.
- Allowing a duel to last for the best of 3 “touches”, or attacks that have dealt at least 1 point of damage.
While in a one-on-one encounter, a creature can take any action, bonus action, or reaction that it would be able to use in a normal combat. However, there are certain restrictions to using such options, as detailed below in Duel Actions.
Alternative Initiative
To reflect the ever-shifting dynamic of a duel, Narrators can choose to implement a different sort of initiative based on the game of rock-paper-scissors. Each participant picks a strategy for the round, depending on which ability score they wish to add to their initiative roll. While many combinations could exist, here is a sample: Powerful (Strength or Constitution), represented by rock; Swift (Dexterity or Intelligence) represented by scissors; or Distracting (Wisdom or Charisma) represented by paper.
At the beginning of each round, the combatants play a brief game of rock-paper-scissors. The winner rolls their initiative with advantage , while on a tie, both participants roll normally. Using this system, a combatant who has high Dexterity may choose a lower ability score in order to try and get an edge against their enemy.
Arena Limitations
The designated area of a one-on-one battle depends heavily on its context. A tournament or formalized bout will almost always have its borders marked, either with paint, turf, or even a ring of shields held by stout warriors from both sides. Regardless, the nature of combat tactics and other one-on-one mechanics mean that participants must stay no more than 30 feet (and often less) from each other. Otherwise, traditional combat may be more fitting for the situation. A one-on-one encounter ends when one creature leaves the borders of the combat, willingly concedes, loses consciousness , or is incapacitated for more than two rounds.
Magic
The tactics discussed here assume melee weapon attacks as the default, but magic is not prohibited by the mechanics. However, the context of the duel may mean use of magic is against the rules, or that certain schools of magic shouldn’t be used. Additionally, while casting does not provoke opportunity attacks , keep in mind that ranged attacks of any kind made within reach of a hostile creature (excluding spectators) are made at disadvantage .
Participants
There is no glory in fighting a far inferior opponent and little sense in fighting an overwhelmingly powerful one. One-on-one combats follow the usual guidelines of combat encounters, using the PC’s level as the party level to calculate the encounter’s difficulty. Ideally, a challenge-based one-on-one encounter should be at least medium difficulty, but should generally be no higher than a hard match-up, especially for a Tier 1 adventurer.
There will always be times when an adventurer challenges an enemy far stronger than themselves, however. In these cases, consider that many NPCs and creatures that would be willing to abide by the rules of one-on-one combat may not seek the death of an opponent, content in proving their superiority. On rare occasions, some deadly foes may be impressed by such an adventurer, letting them live to further improve their skills or even offering to train them.
Because the rules of a one-on-one fight assume a certain amount of mutual understanding, Narrators may rule that creatures with less than 3 Intelligence cannot abide by them and deciding on a case-by-case basis whether a specific creature that has less than 6 Intelligence will or not.
Targeted Attacks
During a duel, when a combatant attacks or casts a spell that targets another creature, they can choose to target a specific part of their opponent’s body once per round, making its attack roll at disadvantage , but inflicting an effect in addition to the normal damage. A targeted attack must be declared before the roll is made. A combatant can’t make a targeted attack if it is already suffering disadvantage on its attack roll, but one that has advantage on its attack rolls instead rolls its targeted attack normally.
Table: Targeted Attacks
| Target | Effect |
| Neck | Target takes additional damage equal to 1d4 x the attacker's proficiency bonus. |
| Head | Target is blinded until the end of its next turn. |
| Arms/Legs |
Target is slowed until the end of its next turn. |
Unusual Body Structures
One of the best things about playing in these worlds is the diversity of creatures one might encounter. That also means that targeting specific body parts may be difficult or even impossible. Similarly, some dueling maneuvers may have the same effect, but be enacted slightly differently depending on an opponent’s anatomy—if a creature is subject to a Knee Strike but doesn’t have conventional knees, some other body part required for locomotion may be damaged.
Duel Actions
Due to the unique advantages and struggles of only focusing on a single opponent, one-on-one combats utilize duel actions in place of the usual action economy. Each combatant gets a number of duel actions on their turn equal to their proficiency bonus which they regain at the beginning of each round. Additionally, a combatant can spend exertion at any time to utilize additional duel actions (1 exertion—1 duel action; 3 exertion—2 duel actions; 5 exertion—3 duel actions). The maximum amount of exertion you can spend this way per round is equal to your proficiency bonus. The cost of common action options is listed below. If a given option is not listed, those that require an action generally cost 2 duel actions, while those that require a bonus action or reaction cost 1. Using movement does not require a duel action, though taking the Dash or Disengage actions costs 2 duel actions as normal.
Using a duel action to perform a combat maneuver does not eliminate its cost—you must still expend exertion as usual. Attacks made as part of a combat maneuver, the Attack action, or the casting of a spell do not require additional duel actions. Finally, you can only take one action and one bonus action per round, and you do not get a reaction each round (unless you pay its duel action cost). However, you can take multiple reactions using duel actions, though this does not allow you to cast more spells in a round than you would otherwise be able to.
Table: Duel Action Cost
| Target | Effect |
| Basic Maneuver | 1 |
| Combat maneuver (bonus action, reaction) | 1 |
| Combat Maneuver (action) |
2 |
| Maintain concentration |
1 |
| Spell (bonus action, reaction) |
1 |
| Spell (action) |
2 |
Additional Exertion
If a combatant doesn’t have an exertion pool or simply finds themselves in need of more points in their existing pool, there are a few ways to gain exertion. One is through the Lend Strength spectator action, where a bystander can grant a combatant temporary exertion. Another is through willingly suffering a level of fatigue or strife . This does not require an action and grants the combatant a number of temporary exertion points equal to their proficiency bonus. This temporary exertion lasts until depleted or the one-on-one combat ends, as detailed in Limitations. Additionally, the maximum number of exertion points (temporary or otherwise) a combatant can have is equal to twice their proficiency bonus. Levels of strife or fatigue suffered in this way are removed at the end of a long rest .
Arena Actions and Environmental Effects
The effects and world actions of many environments (see World Bonuses, Penalties, and Cover in Chapter 8: Combat, Adventurer’s Guide) can also apply to the arenas in which one-on-one encounters take place. While flat ground may be typical in a tournament setting, adventurers are as likely to duel in ruins, through lavish mansions, and any number of other dynamic settings. In the case of a duel, the Narrator should establish any environmental effects (including the placement of any area hazards) at the beginning of the combat.
Once per turn, the Narrator can use a world action as though using a reaction. The target of this world action should be determined randomly, such as by assigning an odd result to one combatant and an even one to the other. Narrators should avoid any world actions that involve other creatures as a participant, but should feel free to use them as a one time effect. For example, a shadow that takes a passing swipe at a combatant and fades away wouldn’t disrupt the dynamic of a one-on-one encounter, but the appearance of a swarm of leeches that joins the combat would.