Combo · ENGINE

813.4.b makes an [Ambush] combat trick FREE TO ATTEMPT - if the Task already running kills your garrison first, the play is UNDONE and the card comes back - and a heal-and-recall save is the one rescue that breaks it

6 cards · calm + body · verified

Pieces

• Vilemaw ×3 UNL-060 · payoff · calm

  [Ambush] (You may play me as a [Reaction] to a battlefield where you have units.) Enemy units here with less Might than me don't deal combat damage. When I hold, draw 1.

• Counter Strike ×3 SFD-194 · enabler · calm/body

  [Reaction] (Play any time, even before spells and abilities resolve.) Choose a unit. The next time that unit would be dealt damage this turn, prevent it. Draw 1.

Payoff

Deck

• Counter Strike is a SIGNATURE card tagged Jax, so 103.2.d.2 forces the legend: measured over data/cards.json on 2026-09-12, the only legend NAME carrying the Jax tag is Grandmaster at Arms, which is Calm/Body and covers Vilemaw's mono-Calm as well. This is a one-legend line and not a domain choice.
• 103.2.d.1 caps a deck at three Signature cards in all, and three Counter Strike spend the whole budget.
• Neither card appears in data/legality.json in any format - checked 2026-09-12.
• You must control at least one unit at the battlefield when Vilemaw's location is chosen at step 2, and still control one when step 5 checks legality. Those are two different moments and the whole entry lives between them.

Run play

• the ambush is the save, if it goes in first

Prerequisites

• THE KEYWORD'S REACTION IS CONDITIONAL, WHICH IS WHY 813.4 GOVERNS IT AT ALL. 822.1.b is functionally 'I may be played to a battlefield where you control Units' AND 'I have [Reaction] as long as I'm being played to a battlefield where you control Units.' The second half is a passive grant with a condition, so 813.4 applies: 'Some passive abilities may grant a card or ability Reaction under certain conditions. The card or ability does not have the Reaction keyword unless and until those circumstances are true.' 822.1.b is cited 61 times in this catalogue; 813.4, 813.4.a and 813.4.b are cited ZERO times (measured 2026-09-12). The keyword has been used everywhere and the paragraph that governs its grant has never been opened.
• THE ORDERING QUESTION, SETTLED FROM THE TEXT AND NOT FILED AS A READING. It does, and there are exactly two: 354.3 ('If another Card Effect or ability is currently resolving, continue resolving it before proceeding with any further steps of this process') and 354.4 ('If there are Tasks outstanding or currently being handled, finish those Tasks before continuing this process'). Neither is a priority window - nobody gets priority in either - which is why it is easy to miss. 333.1 is what makes 354.4 bite: 'Tasks include, but are not limited to: Cleanups, the actions performed during the Start of Turn Process, throughout Combat in its various steps, and the actions performed during the End of Turn Process.' A COMBAT IS A TASK. And 320 confirms the card just sits there: 'While a Cleanup is occurring, Chain Items cannot be Finalized or Resolved.'
• SO THE FAILURE MODE IS REAL AND IT IS THE COMBAT YOU AMBUSHED INTO. Play Vilemaw as a Reaction while the combat you are defending is mid-flight; 354.1 moves him to the Chain and closes the state, 319.1 makes a Cleanup an Outstanding Task after a transition to or from a Closed state, and 354.4 runs the outstanding combat steps and that Cleanup before your play continues. If your garrison at that battlefield dies in it, then at step 5 you no longer control units there, the Reaction grant is false, and 813.4.b fires.
• AND 813.4.b IS WHY THE GAMBLE IS FREE. 'If the chain item does not fulfill the conditions by the time step 5: check legality has been reached, the actions taken while playing it are undone and it is returned to the zone it was played from if it is a card.' The actions taken while playing it INCLUDE the costs, so a failed Ambush costs nothing: 8 Energy and 2 Calm Power come back and Vilemaw returns to hand. 813.4.a is the permission that makes the attempt legal in the first place - 'it can still be played or activated at the appropriate timing as long as doing so could fulfill the conditions.' Every other Reaction play in the pool is spent whether or not it lands; an Ambush is the exception, and no entry has said so.
• WHAT LANDS WHEN IT DOES LAND. A body entering mid-combat takes the Defender designation at the very next Cleanup (319.6 with 323.2.a), before 465.2 resolves, and 143.4's entering exhausted costs nothing on defence because neither 464.2.c.3 nor 465.2.b filters by state. Vilemaw's static then reads on every enemy unit there with less Might than his 8. 417.1.a is the nuance worth stating: 'Assigning Damage during the Combat Damage Step is not Dealing Damage, but will cause Damage to be Dealt when assignment is complete' - so they still ASSIGN under 465.2.c and 465.2.c.4, and then deal none of it. Nothing of yours is damaged at all.
• THE ANTI-SYNERGY, AND IT IS THE WHOLE REASON COUNTER STRIKE IS THE PARTNER. The obvious way to keep your garrison alive through that interposed Task is a would-die save - and every one of the heal-exhaust-recall family is 455, 'A Recall is when a Permanent is relocated from anywhere to its Base without it being a Move.' Saving your last body at that battlefield therefore TAKES IT OFF the battlefield, the Ambush condition is false at step 5, and 813.4.b sends Vilemaw home. OGN-077 Zhonya's Hourglass, the pool's standard answer, breaks this line by rescuing you. Counter Strike does not: 437.4 - 'Damage dealt to a Unit that has that all of that damage Prevented is not considered to have been dealt to it at all' (the doubled 'that all of that' is Riot's own wording, pasted) - generates no kill event and no relocation, so the body is still standing exactly where it was when step 5 asks.
• AND IT CANTRIPS, WHICH MATTERS BECAUSE THE GAMBLE MAY NOT NEED TO BE TAKEN. Counter Strike draws 1, so on a turn where the garrison was never in danger it is a 2 Energy Reaction cantrip rather than a dead card - the same argument that makes the Ambush attempt free, applied to the enabler. Both halves of this line are refundable in their own way, which is unusual enough to be the reason to build it.
• IT IS NOT THE SAME LINE AS counter-strike-tianna-crownguard-in-place-save, WHICH USES THE SAME PROPERTY FOR A DIFFERENT REASON. That entry wants the Prevent because a Recall would switch off a 'While I'm at a battlefield' clause on the saved unit; this one wants it because a Recall would break a DIFFERENT card's play condition while that card is Pending on the Chain. Same paragraph, 455, two unrelated consequences, and neither entry needs the other.
• A DELAYED WOULD-DIE SHIELD IS ENDED BY A BOUNCE, NOT ONLY BY REMOVAL, AND NO SHIELD ENTRY SAID SO (upgrade 2026-09-12, #187 batch 9). 390.5 defines a Delayed LINKED Ability as one that references the generating ability or the Game Objects it affects *"instead of a window of time"* - which is what a *"Choose a friendly unit. The next time it would die this turn"* shield is, against a *"the next spell you play this turn"* delay, which IS a window of time and falls under 391 instead. **390.5.a then has teeth: *"If that Ability affects a Game Object, the Delayed Linked Ability`s window will be as long as that Game Object is in an appropriate zone."*** So returning the shielded body to hand CLOSES the window - and 359.3.e.4 makes the body that comes back a different object, so replaying it does not restore the shield. The cheapest answer in the pool is `OGN-169 Gust` at one Energy; see `windsinger-gust-bounce-as-a-counterspell`, which reaches the same paragraph from the opposite side. Note which half applies before citing 390.5 at all: this project nearly published it against Ravenborn Tome and Raging Firebrand, whose delays are windows of time and therefore 391.
• 437.2 IS WHY 437.4 WORKS, AND IT SITS ONE PARAGRAPH AWAY IN THE SAME BLOCK: "When damage is Prevented, it is replaced with an event where it deals that much damage reduced by the Prevent Value tracked on the Unit specifically." Prevent does not undo damage after the fact - it REPLACES the damage event with a smaller one, and at zero there is nothing left to mark, which is the mechanism behind 437.4's "not considered to have been dealt to it at all." 369.2 puts it beyond argument by naming it: "Some Game Actions are themselves Replacement Effects. Example: Burning Out is a replacement effect. Example: Preventing Damage is a replacement effect." So a Prevent and a heal/exhaust/recall would-die shield are BOTH Replacement Effects and differ in WHICH EVENT they replace - the damage event against the death event - which is the precise reason this line generates no kill event.

Bodies no card supplies

Hold UNL-060 Vilemaw and SFD-194 Counter Strike in hand. Have at least one unit at the battlefield you expect to be attacked; 822.1.b needs it and Vilemaw does not count himself at the moment the location is chosen

Steps

1. Hold UNL-060 Vilemaw and SFD-194 Counter Strike in hand. Have at least one unit at the battlefield you expect to be attacked; 822.1.b needs it and Vilemaw does not count himself at the moment the location is chosen.
2. The opponent attacks. 464.2.c.3 designates attackers and defenders and the combat proceeds as a Task (333.1).
3. Play Vilemaw as a [Reaction] to that battlefield. 354.1 moves him to the Chain and Closes the State; he is Pending (354.2).
4. 354.4 now interposes: any Task outstanding or being handled finishes first - the combat's remaining steps and the Cleanup that 319.1 made outstanding when the state transitioned. 320 keeps your Pending Vilemaw from resolving through it.
5. If your garrison there survives that, step 5 finds the condition true, Vilemaw finalizes, and 319.6 with 323.2.a give him the Defender designation at the next Cleanup - before 465.2 resolves.
6. His static applies: enemy units there with less Might than 8 assign damage under 465.2.c and deal none of it (417.1.a).
7. If instead your last body there is about to die inside that Task, play Counter Strike on it. 437.4 prevents the damage IN PLACE, so the body neither dies nor moves, and the Ambush condition is still true at step 5.
8. Do NOT reach for a heal-exhaust-recall save instead. 455 relocates the rescued body to your BASE, which empties the battlefield and makes the Ambush illegal - 813.4.b then undoes the play.
9. If it does fail, nothing is lost: 813.4.b undoes the actions taken while playing it, refunding 8 Energy and 2 Calm Power, and returns Vilemaw to your hand.
10. Three copies of each (103.2.b), and three Counter Strike spend the entire 103.2.d.1 Signature budget. Nothing here loops and nothing here scores.

Per iteration

one enemy attack at that battlefield deals no combat damage at all, at the price of 8 Energy and 2 Calm Power - refunded in full by 813.4.b if the attempt fails

How it ends

engine only - nothing here scores. One Ambush per copy of Vilemaw (103.2.b) and one Prevent per Counter Strike; a failed Ambush costs nothing but is still one card's worth of timing, and Counter Strike's own draw makes an unused copy a cantrip rather than a dead card

Sources

Published elsewhere

• Riftbound Core Rules, Last Updated 2026-07-16 (data/Riftbound-Core-Rules-2026-07-16.txt), 813.4, 813.4.a and 813.4.b 2026-07-16
• Riftbound Core Rules, Last Updated 2026-07-16 (data/Riftbound-Core-Rules-2026-07-16.txt), 354.1, 354.3 and 354.4 2026-07-16
• Riftbound Core Rules, Last Updated 2026-07-16 (data/Riftbound-Core-Rules-2026-07-16.txt), 333.1 2026-07-16
• Riftbound Core Rules, Last Updated 2026-07-16 (data/Riftbound-Core-Rules-2026-07-16.txt), 319.1 and 320 2026-07-16
• Riftbound Core Rules, Last Updated 2026-07-16 (data/Riftbound-Core-Rules-2026-07-16.txt), 822.1.b 2026-07-16
• Riftbound Core Rules, Last Updated 2026-07-16 (data/Riftbound-Core-Rules-2026-07-16.txt), 437.4 and 455 2026-07-16
• Card text, data/corpus_flat.txt (built from Riot's gallery content API by scripts/build-cards.mjs) 2026-09-12

Walked here, in this project

• Hand walk 2026-09-12 (docs/phase0/walks/2026-09-07-uncited-subrules-500-899.md), batch 19 2026-09-12 record

Walked against Core Rules 2026-07-16

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