Combo · ENGINE

370.1.a.2 and 465.2.c.1.a - two different paragraphs make damage simultaneous, and a sweep is the SPELL one

3 cards · mind + body · verified

Pieces

• Keeper of Masks ×1 UNL-081 · enabler · mind

  [Hidden] (Hide now for 1 Power of any domain to react with later for 0 Energy.) [Temporary] (Kill me at the start of my controller's Beginning Phase, before scoring.) When you play me, play two Reflection unit tokens here. Then do this: They become copies of me.

• Flurry of Blades ×1 OGN-133 · engine · body

  [Reaction] (Play any time, even before spells and abilities resolve.) Deal 1 to all units at battlefields.

• Spectral Centaur ×1 UNL-068 · payoff · mind

  When another friendly unit dies, give me +2 Might this turn.

Payoff

Deck

• Keeper of Masks and Spectral Centaur are mono-Mind and Flurry of Blades is mono-Body, so 103.1.b.1 needs a Body/Mind legend - and the census run against data/cards.json on 2026-09-12 returns exactly ONE NAME: Defender of Tomorrow (VEN-149/VEN-194). This is a forced shell and there is no second option.
• No card here is Signature (data/cards.json, signature=false on all three) and none appears in data/legality.json in either format - checked 2026-09-12.

Prerequisites

• TWO DIFFERENT PARAGRAPHS MAKE DAMAGE SIMULTANEOUS AND THEY COVER DIFFERENT SOURCES - THIS IS THE ENTRY'S POINT. For a spell or ability it is 370.1.a.2: 'An event can occur simultaneously with other events only when those events are all the result of the same Game Action or change in state occurring', whose worked example is a spell killing two units at once 'because their deaths result from the same game action.' For the Combat Damage Step it is 465.2.c.1.a: 'When all Damage is assigned, it will be Dealt simultaneously. These actions are not synonymous.' Both were cited by nothing. A one-Energy sweep like Flurry of Blades runs on the FIRST of them, not the second - the standing shorthand in this project attributes it to the combat rule, and that is the wrong paragraph.
• 465.2.c.1 IS THE COMPANION AND IT IS WHY A SWEEP MUST BE PLAYED BEFORE ASSIGNMENT. 465.2.c.1: 'Assigning Damage is not Dealing Damage.' 417.1.a says it for the step - 'Assigning Damage during the Combat Damage Step is not Dealing Damage, but will cause Damage to be Dealt when assignment is complete' - and 417.3.a, also uncited, says it from the Damage block: 'Assigning Damage causes Damage to be dealt outside of being directed to Deal Damage.' So there is NO window between assignment and dealing. A [Reaction] played 'in response to the damage' does not exist; 465.2.c reads each side's summed Might at assignment, and the Centaur's bonus has to be on him before that moment.
• WHICH IS EXACTLY WHEN YOU PLAY IT. Flurry of Blades is [Reaction] (813.1.c.1), so it goes in the Showdown before the Combat Damage Step. The three bodies die, 370.1.a.2 makes it one batch, 383.3.d lets you order the three triggers, and the Centaur stands at Might 11 when 465.2.c assigns. Played one step later it would be worth nothing at all.
• THE FODDER IS FREE BECAUSE IT IS ALREADY CONDEMNED. 811.1.b hides Keeper of Masks for one rainbow Power and its tail gives him '[Reaction] and you may play this, ignoring its base cost' from the next turn, so the three bodies cost ONE Power and no Energy; 811.1.d.1 puts him at that battlefield, which is where Flurry of Blades can reach him ('all units at battlefields' does not touch a base). And 816.1.b kills every one of them at the start of your next Beginning Phase anyway, so the sweep spends bodies that were going to die regardless - the cheapest possible feed for a death counter.
• THE ARITHMETIC, WITH THE QUANTITIES DECLARED. Keeper of Masks is Might 1 and the two Reflections are Might 0, because R27 on issue #11 settled that Might is not a copyable trait - 477.1.a lists the inherent traits without it and 477.1.b.1.a lists the copyable traits without it. 143.2.a kills on 'nonzero damage marked on it equalling or exceeding its Might', so one damage kills all three: 1 >= 1 and 1 >= 0. Three friendly deaths, +2 each, Spectral Centaur goes from 5 to 11 for the turn. Every enemy body at 1 Might or less dies in the same action.
• AND NO CASCADE, WHICH IS 383.4.a.4 READ THE OTHER WAY. The two Reflections copy Keeper of Masks, whose only text besides its keywords is 'When you play me, play two Reflection unit tokens here' - a Play Effect by 383.4.a, and the Reflection token prints that it does not get those. 383.4.a.4 ('Abilities that trigger when another object is played are not considered Play Effects') is what draws the line, and here it falls on the losing side: three bodies, not seven.
• WHAT THE SWEEP COSTS YOU BESIDES THE FODDER. Flurry of Blades is symmetric over every battlefield, so any OTHER friendly body of yours at 1 Might or less dies too, and the Centaur is paid for those as well - which is upside only if you meant to spend them. The Centaur takes 1 damage himself and survives at 5; 143.3.b heals it at the end of the turn. Mind prints no 1-Might fodder of its own: every Mind token in the pool is a 3 Might Sprite or Mech (swept over data/corpus_flat.txt, 2026-09-12), which is precisely why Keeper of Masks and his 0 Might copies are the enabler and not a Sprite package.
• THE SHORTFALL, STATED PLAINLY: nothing here scores. The product is one oversized attacker for one turn plus a board wipe of everything at 1 Might, for 1 Energy, 1 rainbow Power and a 6-Energy body that has to already be out. 317.2.c expires the +6 at cleanup, so it has to be cashed in the combat it was made for. 103.2.b caps each card at three, and a second Keeper of Masks is a second three-body batch but needs a second battlefield, since 811.1.b hides at a battlefield 'that doesn't already have a facedown card hidden there' and a Duel puts two on the table (485.4).
• IF YOU HAVE TWO COMBATS, 461.1 IS THE FREE HALF: 'If more than one Battlefield has Units controlled by opposing players at it at the same time, the Turn Player decides which Combat to resolve first.' Resolve the combat you are losing first, let its deaths pay the Centaur, and the second combat's 465.2.c assignment reads him at his new Might. That works because 465.2.c.1.a finishes the first combat's damage in one simultaneous batch before the second begins - the combat half of this entry's own split.
• ANTI-SYNERGY WORTH NAMING, BECAUSE THE SAME EVENT PAYS THREE DIFFERENT WAYS. Measured over data/corpus_flat.txt on 2026-09-12, the pool has exactly five 'a friendly unit dies' payoffs and the wording splits them: UNL-068 Spectral Centaur and UNL-129 Vicious Snapjaws have no gate and collect the whole batch; SFD-169 Altar of Memories is rationed by its own exhaust and pays ONCE however many die; OGN-118 Wraith of Echoes and UNL-174 Shard of Undoing say 'the first time ... each turn', which 383.1.b collapses to one execution. Simultaneity is worth a great deal to the first pair and nothing to the other three.

Steps

1. Have Spectral Centaur on the board (E6) and hide Keeper of Masks at a battlefield you control for one rainbow Power (811.1.b).
2. On a later turn, attack into a garrison. In the Showdown, play Keeper of Masks from face down for 0 Energy - 811.1.b's tail gives him [Reaction] - and 811.1.d.1 puts him at that battlefield with two Reflection tokens beside him.
3. R27 leaves the Reflections at 0 Might and 383.4.a.4 gives them no cascade: Keeper's own text is a Play Effect and the Reflection does not get it.
4. Still before the Combat Damage Step, play Flurry of Blades for 1 Energy as a [Reaction] (813.1.c.1): one Deal action, 1 damage to every unit at every battlefield.
5. 143.2.a kills Keeper of Masks at Might 1 and both Reflections at Might 0, and every enemy body at 1 Might with them. 370.1.a.2 makes all of it one simultaneous batch, because it is one game action.
6. 383.3.d lets you order the three Spectral Centaur triggers; each gives +2 this turn, so he stands at Might 11.
7. 465.2.c then assigns - and only then, because 465.2.c.1 and 417.1.a keep assignment and dealing apart with no window between them. The Centaur's 11 is in the sum; 465.2.c.1.a deals both sides' damage simultaneously.
8. If a second battlefield is also in combat, 461.1 lets you resolve this one first so its deaths are already paid when the other assigns.

Per iteration

three condemned friendly bodies converted into +6 Might on the one unit that survives them, in the same instant as a board-wide 1-damage sweep

How it ends

engine - one Spectral Centaur at Might 11 instead of 5 for a single turn, plus every enemy unit at 1 Might or less killed, for 1 Energy and 1 rainbow Power on top of a 6-Energy body already in play. 317.2.c expires the bonus at cleanup and nothing here scores

Sources

Published elsewhere

• Riftbound Core Rules, Last Updated 2026-07-16 (data/Riftbound-Core-Rules-2026-07-16.txt) 2026-07-16

Walked here, in this project

• Hand walk 2026-09-12, issue #187 - uncited Core Rules sub-rules 300-499 2026-09-12 record

Walked against Core Rules 2026-07-16

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