What do Action and Reaction mean?

Most cards in Riftbound: the League of Legends trading card game can be played at one moment only: in your own Main Phase, while nothing else is going on. Action and Reaction are the two keywords that lift this limit. They are printed on a colored highlight in a card's text, and they never change what the card does. They only change when you may play it.

Reaction includes everything Action allows and adds one more moment. Both keywords appear mostly on spells, but units, gear and abilities carry them too. The Action keyword has nothing to do with the Action Phase, the name the Proving Grounds How to Play booklet gives the Main Phase.

When can a card without Action or Reaction be played?

A card without either keyword can be played only in your own Main Phase, while no showdown or combat is going on and nothing waits on the Chain. This is the default timing set by rule 310.1.a of the Core Rules, and most units and gear follow it, as do spells such as Vengeance, which kills a unit. An ability written as a cost, a colon and an effect keeps the same timing unless it has Action or Reaction.

What does Action let you do?

Action lets you play a card during a showdown as well, on your own turn or on your opponent's. A showdown opens when units move to a battlefield their player does not control, and every combat opens with one. In a showdown the players act one at a time, and the rules call the right to act Focus. The player who moved in has it first, and the player with Focus may play one card or ability with Action or Reaction, or pass.

Action spells are mostly tricks for fights. Hextech Ray deals 3 damage to a unit at a battlefield, Punch First gives a unit +5 Might for the turn, and Rune Prison stuns a unit, so it deals no combat damage this turn. When your opponent attacks one of your battlefields, you can stun their biggest attacker with Rune Prison once the showdown reaches you.

Action does not let you answer a spell or ability that has just been played. While something waits on the Chain, only cards and abilities with Reaction can be played, as rule 309.1.a says.

What does Reaction add?

Reaction lets you play a card at every moment Action does, and also while something else waits on the Chain, so you can answer a spell or ability before it takes effect. The reminder text on Reaction cards reads "Play any time, even before spells and abilities resolve."

Every spell and every ability waits on the Chain before it resolves, apart from abilities that add Energy or Power, and the newest item resolves first. Units and gear go onto the board as soon as they are played, so only the abilities they set off can be answered. Suppose your opponent plays Hextech Ray on your unit with 2 Might. In answer, you play Discipline, which gives a unit +2 Might this turn and draws you a card. Discipline resolves first, so your unit has 4 Might when the 3 damage arrives, and it survives. Wind Wall would counter Hextech Ray instead, and Not So Fast counters an enemy spell or ability that chooses one of your units or gear. If your opponent answers your Discipline in turn, that answer sits on top of it and resolves first, and the same holds for every answer after that.

"Any time" has a limit. On your opponent's turn you cannot play a Reaction out of nothing, because while their Main Phase runs with no showdown and nothing on the Chain, only they may start playing cards. Your chance comes when they play a spell, use an ability or set off a triggered ability, or when you have Focus in a showdown.

Can units, gear and abilities have Action or Reaction?

Yes. Rules 806 and 813 of the Core Rules allow both keywords on cards and on the abilities of units, gear, Legends and runes.

• Units. Shen, Kinkou has Reaction, so you can play him while your opponent attacks one of your battlefields, and he joins the fight as a defender with Shield 2 and Tank. He must still be played to your base or to a battlefield you control, as every unit must.
• Abilities. On an ability, the keyword is printed in front of the cost. Shadow, a unit from Unleashed, has an Action ability that stuns an enemy unit attacking at its battlefield, so it is used during the showdown of a combat.
• Gear. Equipment with Quick-Draw, such as Long Sword, has Reaction and attaches itself to one of your units as it is played.
• Runes. The two abilities of every basic rune, exhausting it for 1 Energy and recycling it for 1 Power, both have Reaction, which is what lets you pay for a card on your opponent's turn. They resolve at once and cannot be answered.

Can a card gain Action or Reaction during a game?

Yes. Some rules and cards give the keyword to a card while a condition holds, and only for as long as it holds.

• A card with Hidden that you hid facedown at a battlefield gains Reaction from the next turn on, and you may play it from there without paying its base cost.
• A unit with Ambush, such as Vilemaw, has Reaction while it is played to a battlefield where you already have units.
• Kai'Sa, Rebel from Radiance, the fifth set, with its release on 23 October 2026, gives all your spells Reaction while she is in a showdown.
• Jarvan IV, Martial Paragon, also from Radiance, gives your gear with Deploy the Action keyword.

Why should you leave runes ready at the end of your turn?

An Action or Reaction played on your opponent's turn has to be paid for with the runes you still have ready. Your runes are readied again only in your own Awaken Phase, unless a card readies them, and every rune pool empties at the end of each turn. The runes you leave ready when you end your turn are your whole budget until your next one.

Holding runes back is a trade, and it pays off only when you hold a card that is worth more on the other turn, such as a counter or a combat trick. Your opponent sees your ready runes too, and an experienced player will expect a Reaction and play around it.

Timing matters most on spells, because the same 3 damage plays very differently on your own turn and in the middle of your opponent's attack, and that is why the question of when you can play a spell has a different answer for each keyword. The spells page lists the spells of every set, Action and Reaction spells among them, and the full wording of both keywords is in rules 806 and 813 of the Core Rules on Riot's Rules Hub.