How Do Reactions Work in Dungeons and Dragons (D&D) Fifth Edition (5E)

Above all else, D&D has always been a combat game. The Combat System in Dungeons and Dragons has always taken up 3/4 of the rules, with actions, and attacks, reactions, counterspells, grappling and movement constantly confusing and confounding new players. In order to get the most out of Combat you have to understand how the Action Economy works (Composed of Actions, Bonus Actions and Reactions). Today we’re focusing on Reactions!

Reactions are an interesting subset of Actions because they are the only action to not take place on your turn. A Reaction, instead, is exactly what it sounds like. It is an action you take to react to a certain situation, such as an Attack of Opportunity, a spell that reduces the amount of damage you took or something else altogether.

What is a Reaction and How Does it Work!

A Reaction is a special Action you take when it is not your turn in Combat. Every character and Monster gets one Reaction per round. If you have spent your Reaction, you don’t get another one until the start of your turn. YOU DO NOT GET REACTIONS BACK AT THE TOP OF THE ROUND! This is a common misconception. If you spend your Reaction, you get a new one at the start of your turn.

One of the most common Reactions is the Attack of Opportunity mentioned above. If an enemy moves out of an area that you threaten (an area that you can hit with an attack, usually an adjacent space to your character) they provoke an Attack of Opportunity. If you have not used your reaction, you can make a single attack against them as a Reaction. An enemy does not Provoke if they have taken the Disengage action. A character can make only a single melee weapon attack when making an Attack of Opportunity unless they have a Class Feature that allows for something different, or if they have the War Caster feat, which allows them to cast a spell with a casting time of one action that hits only the target that Provoked the Attack of Opportunity.

A second method of using your Reaction, which anyone can use, is Ready an Action. A character Readies an Action by taking the Ready Action on their turn, when they do so, they give an example of what their character is Readying (Such as a spell, or an attack) and at what time. For example, say an enemy is hiding behind a pillar with a bow, and they keep moving out and attacking and then ducking behind the pillar again, making it very difficult to hit them. You could Ready an Action to cast Scorching Ray at them the next time they emerge from their hiding place. The next time the archer moves into view, your Readied Action goes off automatically as a Reaction, which means before the Archer gets to attack, you hit them with your Scorching Ray spell.

Readying an action is an oft underused method of hitting hiding opponents, or controlling the battlefield. For example, say your enemies are spread out, you could Ready an Action to cast Lightning Bolt, once more than one enemy is in a line that you can see. On the next enemy’s turn, if they move across the battlefield and line up with another enemy, you could hit them then, getting more than one enemy at once. Similarly, you could Ready an Action to Cast Wall of Fire or Wall of Force once your enemies have situated themselves in an advantageous situation to separate them.

Special Class Ability Reactions

Many classes get extra Reaction based abilities that they can use to their advantage. The Rogue gains Uncanny Dodge that they can use to half the damage on any attack that they can see. Some fighters can use their reaction to protect nearby allies with their shields, giving the enemy disadvantage. Spellcasters have certain spells that they can use, such as Featherfall when they are falling off a cliff. Shield, to increase their AC when they are being attacked. Counterspell, if an enemy spellcaster is about to cast a spell within their range. Absorb Elements can give you resistance to a certain damage type when you are about to be hit by a Fireball or Dragon’s Breath Weapon attack.

Feats such as War Caster increase the ways you can use your Reaction by allowing you to Cast Spells as an Attack of Opportunity instead of making a melee attack. Defensive Duelist allows you to add your Proficiency Bonus to AC and potentially cause a creature to miss you as a Reaction. Mage Slayer allows you to make attacks against creatures who cast spells within 5 feet of you, potentially causing them to lose Concentration on their spell. Shield Master allows you to use your reaction to duck behind your shield, taking no damage on a Dexterity save that you would normally take half damage from on a success.

Take a look at your abilities and see if any of them allow you to make use of your Reactions. I, personally, suggest separating your class abilities on your character sheet or on scrap paper or online software into Actions, Bonus Actions and Reactions, so that you know which abilities you can use and when!

If you're looking for more guides to D&D, check out the links below!

• A Guide to Legendary and Lair Actions
• A Guide to Initiative
• A Guide to Bonus Actions