Rules Ruling · Timing
When Can You Play a Reaction? Timing and Priority Windows Explained
“When can I play this?” is the most common timing dispute at the table. The 2026-07-16 Core Rules split the turn into four states, and the Reaction keyword is the key that opens those windows — it is what lets you act on an opponent’s turn. Where the official FAQ differs from the CR, the FAQ takes precedence; both are cited here.
Citations: CR 2026-07-16 §308–310（回合狀態）、§312.2（攞優先權時機）、§337–340（FEPR）、§359.3.c（反應窗口）、§429.2.a、§429.3（Add 反應）、§813（Reaction 關鍵字）· Vendetta FAQ 2026-08-14（Fallen Feline 判例；FAQ 優先於 CR）
What Reaction is
Reaction is a permissive keyword that can appear on cards, rune abilities, legend abilities and permanent abilities (CR 813.1.a). It grants everything Action grants (CR 813.1.b) and is functionally short for “this can be played or activated during Closed States, on any player’s turn” (CR 813.1.c). It is printed as [Reaction] on cards and [Reaction][>] on abilities (CR 813.1.d). It is permission only — it does not alter what the card does (CR 813.3).
The four turn states
The turn is always in exactly one of four states (CR 308–310):
- Neutral Open: no Showdown/Combat, no chain. By default only the turn player, with priority in their own Main Phase, can play cards (CR 310.1.a, 316.5.b).
- Neutral Closed: no Showdown/Combat, a chain exists. Only cards and abilities with Reaction can be played or activated (CR 309.1.a).
- Showdown Open: a Showdown or Combat is in progress, no chain. Only Action or Reaction cards and abilities can be played (CR 308.1.a).
- Showdown Closed: a Showdown or Combat is in progress and a chain exists. Again, only Reaction plays (CR 309.1.a).
How the reaction window works
After a spell is finalized, other players get a chance to play Reactions before it resolves (CR 359.3.c). The FEPR process governs the rest: items finalize oldest-first (CR 337.1.b), resolve newest-first (CR 340.1), and priority passes in turn order after each item (CR 337.4, 340.4, 312.2.c–d). Only when all players pass in sequence does the top item resolve (CR 339.1).
Add Reactions: even mid-cost-payment
Activated abilities that add resources and have the Reaction tag can be activated any time resources must be paid — including during the pay-costs step of playing a card, and even with no priority window (CR 429.3). They finalize and resolve immediately (CR 429.3.a) and do not move Priority or Focus (CR 429.2.a).
FAQ
My opponent plays a card on my turn — how do I answer it?
Their card goes on the chain and the turn becomes Closed. Priority then passes in turn order; when you receive it (CR 312.2.d) you may play a Reaction card or activate a Reaction ability (CR 309.1.a). The top item only resolves after all players pass in sequence (CR 339.1).
When can I play a card without [Reaction]?
By default only the turn player, with priority in their own Main Phase in a Neutral Open state (CR 310.1.a, 316.5.b). Closed States (CR 309.1.a) and Showdown States (CR 308.1.a) are off-limits unless card text grants permission.
Can I activate an “Add” reaction while paying costs if I come up short?
Yes. Add abilities with the Reaction tag can be activated any time resources must be paid, including the pay-costs step, and finalize and resolve immediately (CR 429.3, 429.3.a).
When can I react to Fallen Feline naming a spell?
Per the official FAQ: you can react to Fallen Feline’s play effect (its triggered ability) before a spell is named. Once the ability resolves and the name is chosen, opponents can’t put spells with that name onto the chain; spells already on the chain are unaffected.
Can a unit with Reaction be played anywhere?
No. Reaction is only timing permission — a unit can still only be played to your base or a battlefield you control (CR 813.3.a).
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