Combo · ENGINE

The same doubled Deathknell as the Chaos version, one-sided and in a domain pair with four legends instead of one

6 cards · mind + order · verified

Pieces

• Ruined Rex ×3 UNL-067 · payoff · mind

  [Deathknell][>] Deal 4 to an enemy unit. (When I die, get the effect.)

• Karthus, Eternal ×3 OGN-236 · engine · order

  Your [Deathknell] effects trigger an additional time.

Payoff

Deck

• Mind + Order: Ruined Rex is mono-Mind and Karthus mono-Order (103.1.b.3), so 103.1.b.2 needs a legend covering both, and the census prints four such names - SFD-201/SFD-249 Chem-Baroness, UNL-199/UNL-235 Deceiver, OGN-265/OGN-308 Herald of the Arcane, OGS-021 Lady of Luminosity - Starter.
• Neither card is banned or restricted in either format, and neither is a Signature card.
• A way for the Rex to die on your terms. Combat does it for free; a sacrifice outlet does it on schedule.

Prerequisites

• WHAT A DEATHKNELL IS, IN ONE PARAGRAPH. 808.1.c: 'It is functionally short for "When I die, [Effect]."' 808.1.d: 'The Trigger for this and similar effects that trigger on their source's death is the Permanent being Killed and sent to the Trash.' 808.2: 'Each instance of Deathknell a Permanent may have will trigger separately', with 808.2.a giving the controller the order. Karthus adds an instance, so one death is two separate 'Deal 4' executions - and each one chooses its own target, so it is 4 and 4 on two bodies or 8 on one.
• AND WHY IT IS TWO DEAL ACTIONS RATHER THAN ONE BIG ONE. 715.2: 'If the Deal action has multiple targets, the amount of Damage dealt to each target is increased by Bonus Damage individually and separately.' Two executions are two Deal actions, so a Bonus Damage source pays each of them - which is the opposite of a single 'deal 8', where it pays once. That is the same arithmetic that makes a six-Deal spell the pool's maximum for the family.
• THE COMPARISON THAT JUSTIFIES THE ENTRY, STATED RATHER THAN IMPLIED. blade-kogmaw-karthus-wipe already walks Karthus with a damage Deathknell - OGN-190 Kog'Maw, Caustic, 'Deal 4 to all units at my battlefield', 3 Energy + 1 Power for a 1 Might body. It is cheaper and it is a sweeper. Two things separate this entry from it and both are checkable: Kog'Maw is CHAOS, so that line needs Chaos + Order and the census prints exactly ONE such legend name (VEN-155 / VEN-197 Heart of the Tempest), where Mind + Order prints four; and Kog'Maw's sweep says 'all units', which includes yours, while the Rex says 'an ENEMY unit'. You pay 3 more Energy for a one-sided effect and a shell with four legends.
• THE ANTI-SYNERGY IS EXACT AND IT IS EASY TO BUILD BY ACCIDENT. 808.1.d.1: 'If the Permanent with the effect is not sent to the Trash, for example because its "killed" event was replaced with a recall, the triggered ability will be removed from the chain' - and Riot's worked example is a Zhonya's Hourglass save. So every heal/exhaust/recall shield in the deck switches this off, including OGN-269 The Boss as a legend and OGN-077 Zhonya's Hourglass as a gear. A Deathknell deck cannot also be a protection deck.
• KARTHUS IS ONE OF THREE, AND THE OTHER TWO DO NOT REACH THIS. The pool's trigger multipliers are OGN-236 Karthus, Eternal (Deathknell), UNL-029 Red Brambleback (conquer here) and UNL-087 Blue Sentinel (hold here) - swept over all base codes for 'trigger an additional time'. Neither of the other two touches a death, so this family scales by Karthus copies and by nothing else. Two Karthus make it three executions, not four: each adds one instance to the same ability (808.2).
• THE LEDGER, WITH THE QUANTITIES DECLARED. Karthus 3 Energy + 1 Power, Ruined Rex 6 Energy + 1 Power. One Rex death under one Karthus is 8 damage, split as you like; under two Karthus it is 12. 143.2.a kills on marked damage at or above Might, so 4 removes a Might-4 body and 8 removes almost anything in the pool. Three of each by 103.2.b.
• WHAT IT IS NOT. Nothing here scores; 469 defines Scoring as Conquer or Hold. And the damage is dealt by the ability, not by a unit, so 417.6.b.3's Challenge exception does not apply and a blanket spell-and-ability fog DOES stop it.

Steps

1. Play Karthus, Eternal (3 Energy + 1 Power) and Ruined Rex (6 Energy + 1 Power).
2. Let the Rex die - in combat, or to a sacrifice outlet you already run.
3. 808.1.d makes the death the Trigger; Karthus adds a second instance and 808.2.a lets you order them.
4. Each execution deals 4 to an enemy unit of its own choosing: 4 and 4 on two bodies, or 8 on one.
5. Do NOT run a heal/exhaust/recall shield on the Rex - 808.1.d.1 removes the trigger from the chain if he never reaches the Trash.
6. A second Karthus makes it three executions (808.2 adds one instance each), not four.

Per iteration

8 damage split freely across enemy units per Ruined Rex death under one Karthus, 12 under two

How it ends

engine only - three of each card by 103.2.b, and every execution needs a fresh Rex death; 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
• Card text verbatim from data/corpus_flat.txt (built from Riot's gallery content API) 2026-09-07

Walked here, in this project

• Hand walk 2026-09-07 (docs/phase0/walks/2026-09-07-uncatalogued-calm-mind-order.md, batch 3) 2026-09-07 record

Walked against Core Rules 2026-07-16

Match a deck list against the whole catalogue