Combo · ENGINE

740.2.b needs both units alone — Cataclysmic Duel makes that the whole board, and Fiora doubles for the rest of the game

2 cards · body · verified

Pieces

• Cataclysmic Duel ×1 VEN-090 · engine · body

  Each player chooses a unit they control. Kill the rest.

• Fiora, Peerless ×1 SFD-110 · payoff · body

  When I attack or defend one on one, double my Might this combat.

Payoff

Deck

• Any legend with Body among its two domains (103.1.b.3) — 17 names: Relentless Storm (OGN-249), Blind Monk (OGN-257), Bounty Hunter (OGN-267), The Boss (OGN-269), Wuju Bladesman - Starter (OGS-019), Might of Demacia - Starter (OGS-023), Purifier (SFD-183), Grandmaster at Arms (SFD-193), Battle Mistress (SFD-203), Grand Duelist (SFD-205), Pridestalker (UNL-183), Wuju Master (UNL-191), Voidreaver (UNL-201), Keeper of the Hammer (UNL-203), Butcher of the Sands (VEN-141), Defender of Tomorrow (VEN-149), Matriarch of War (VEN-153).
• 8 Energy and 3 Body Power, which is the most expensive spell in the Body population — see the last notable before building for it.

Prerequisites

• 'ONE ON ONE' IS DEFINED, AND THE DEFINITION IS TWO CONDITIONS, NOT ONE. 740.2.b: 'A unit is one on one when it and the enemy unit at the same location are both alone', with 740.2.a: 'A unit is alone when there are no other friendly units at the same location.' So Fiora needs BOTH sides reduced to a single body at that location — a garrison of two of yours breaks her clause just as surely as a garrison of two of theirs. That is why she is hard to switch on and why a board-wide reset is the natural enabler rather than a combat trick.
• CATACLYSMIC DUEL SETS EXACTLY THAT STATE, AND PERMANENTLY. 'Each player chooses a unit they control. Kill the rest' leaves one unit per player on the whole board, so every combat that happens afterwards is one on one until somebody rebuilds. Fiora at 3 Might fights at 6, attacking or defending, from that moment on.
• AND THE SPELL TARGETS NOTHING. 355.10.e: an object 'part of a set of objects chosen in whole or in part by other players' is not a target, and its worked example is exactly this wording — '"Each player kills a unit they control" does not target. Each player, including the one who played the spell, chooses a unit to kill as the spell or ability resolves.' So [Deflect] never charges (809.1.c and 809.1.d pay only for targeting or choosing) and no 'can't be chosen by enemy spells and abilities' clause — `SFD-105 Ruin Runner`'s, for instance — keeps a body alive through it.
• THE OPPONENT PICKS THEIR SURVIVOR, WHICH IS THE ENTRY'S REAL RISK. They keep their best body, so the duel Fiora inherits is against the largest thing they had. At 6 Might she beats a 5 and loses to a 7; 465.2.c.3 forces lethal onto one unit before the next, so there is no splitting. Price the line as 'my 6 against their best', not as 'my 6 against a leftover'.
• Gear survives the wipe — the spell kills units — so an Equipment already attached to Fiora is still on her afterwards, and 434.1.d modulates her Might by its Might Bonus BEFORE the doubling, which is where the line actually scales: `SFD-102 Hexdrinker` (M+1) or `VEN-073 Jagged Cutlass` (M+2) make her 4 or 5 base and so 8 or 10 in the duel.
• Priced whole: 8 Energy + 3 Body Power for the reset, on a 3 Energy + 1 Body Power Fiora already in play. It is a reset you cast when behind on board, and the doubling is what stops the rebuild being symmetric.
• AN "ATTACK OR DEFEND" TRIGGER FIRES TWICE PER TURN CYCLE, AND THIS ENTRY PRICED IT AT HALF RATE (citation upgrade 2026-09-12, #187/300-499 lane). 383.4.e defines an Attack Trigger as firing when a Unit or PLAYER gains the Attacker designation for the first time during a combat, and 383.4.f is the identical sentence for the Defender - so a card worded *"when I attack or defend"* satisfies BOTH definitions and is an Attack Trigger AND a Defend Trigger, exactly the shape the rules state outright for the other pair at 823.1.b (*"Hunt is both a Conquer and a Hold effect"*). The honest rate is once on your turn attacking and once on theirs defending. Measured across the catalogue on 2026-09-12, SIX entries use an attack-or-defend card and not one cited both paragraphs. Two limits that keep it from running away: 383.4.e.2.a checks the condition ONCE PER COMBAT despite a unit gaining and losing the designation several times in it (383.4.f.2.a is the mirror), so blinking a carrier out of a combat and back re-fires nothing; and the whole attack side is UNIT-keyed - the pool prints ZERO cards worded *"when you attack"* against FOUR on the defend side, three of them battlefields - which is why a battlefield can carry a defend trigger at all and never an attack one.

Steps

1. Play Fiora, Peerless (3 Energy + 1 Body Power).
2. When the board is crowded — ideally when you are behind on bodies — cast Cataclysmic Duel (8 Energy + 3 Body Power).
3. Each player chooses one unit they control; choose Fiora. Everything else dies. 355.10.e means nothing was targeted, so [Deflect] and 'can't be chosen' clauses do not intervene.
4. The board now holds one unit per player, so 740.2.a makes each of them alone and 740.2.b makes any combat between them one on one.
5. Attack or defend with Fiora: her Might doubles for that combat (3 becomes 6, or 8/10 if she is carrying a Might Bonus, 434.1.d).

How it ends

engine — a board reset to one unit a side, after which Fiora fights at double Might in every combat until somebody rebuilds; 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 2026-09-07, issue #173 — the uncatalogued Fury / Body / Chaos cards 2026-09-07 record

Walked against Core Rules 2026-07-16

Match a deck list against the whole catalogue