Confidence:StrongSolidPlausibleTentativeSpeculative

• Splinter Twin✓

  2RR

  Enchantment — AuraR

  Copy chain: one card creates hasty copies of a creature whose ability or ETB the partner exploits — the canonical Kiki-Jiki / Splinter Twin pattern.
• Kiki-Jiki, Mirror Breaker✓

  2RRR

  Legendary Creature — Goblin ShamanR

  Copy chain: one card creates hasty copies of a creature whose ability or ETB the partner exploits — the canonical Kiki-Jiki / Splinter Twin pattern.
• Ral Zarek

  2UR

  Legendary Planeswalker — RalRU

  Both cards produce extra combat steps — their effects stack.
• Saheeli, the Sun's Brilliance

  UR

  Legendary Creature — Human ArtificerRU

  Copy chain: one card creates hasty copies of a creature whose ability or ETB the partner exploits — the canonical Kiki-Jiki / Splinter Twin pattern.
• The Jolly Balloon Man

  1RW

  Legendary Creature — Human ClownRW

  Copy chain: one card creates hasty copies of a creature whose ability or ETB the partner exploits — the canonical Kiki-Jiki / Splinter Twin pattern.
• Feldon of the Third Path

  1RR

  Legendary Creature — Human ArtificerR

  Copy chain: one card creates hasty copies of a creature whose ability or ETB the partner exploits — the canonical Kiki-Jiki / Splinter Twin pattern.
• Tempestra, Dame of Games

  1R

  Legendary Creature — Elemental IllusionR

  Copy chain: one card creates hasty copies of a creature whose ability or ETB the partner exploits — the canonical Kiki-Jiki / Splinter Twin pattern.
• Orthion, Hero of Lavabrink

  3R

  Legendary Creature — Human SoldierR

  Copy chain: one card creates hasty copies of a creature whose ability or ETB the partner exploits — the canonical Kiki-Jiki / Splinter Twin pattern.
• Jaxis, the Troublemaker

  3R

  Legendary Creature — Human WarriorR

  Copy chain: one card creates hasty copies of a creature whose ability or ETB the partner exploits — the canonical Kiki-Jiki / Splinter Twin pattern.
• Baron Helmut Zemo

  BBB

  Legendary Creature — Human Noble VillainB

  Copy engine: one card makes a copy of a creature every turn, and the other's enter-the-battlefield effect rewards each copy. Real, repeatable value — the partner can't untap or re-enter the copier, so it never goes infinite.
• Chandra, Flameshaper

  5RR

  Legendary Planeswalker — ChandraR

  Copy engine: one card makes a copy of a creature every turn, and the other's enter-the-battlefield effect rewards each copy. Real, repeatable value — the partner can't untap or re-enter the copier, so it never goes infinite.
• Bruce Banner // The Incredible Hulk

  U2RRGG

  Legendary Creature — Human Scientist Hero // Legendary Creature — Gamma Berserker HeroGRU

  Both cards produce extra combat steps — their effects stack.
• Terra, Magical Adept // Esper Terra

  1RG

  Legendary Creature — Human Wizard Warrior // Legendary Enchantment Creature — Saga WizardBGRUW

  Copy engine: one card makes a copy of a creature every turn, and the other's enter-the-battlefield effect rewards each copy. Real, repeatable value — the partner can't untap or re-enter the copier, so it never goes infinite.
• All-Out Assault

  2RWB

  EnchantmentBRW

  Both cards produce extra combat steps — their effects stack.
• Aggravated Assault

  2R

  EnchantmentR

  Both cards produce extra combat steps — their effects stack.
• Soulherder

  1WU

  Creature — SpiritUW

  Blink pair: one card can blink creatures repeatedly, and the other's ETB rewards every re-entry. Free-running only when the blink is free or refunded (Deadeye + Drake class); otherwise a repeatable value engine.
• The Mind Stone

  1W

  Legendary Artifact — Infinity StoneW

  Blink pair: one card can blink creatures repeatedly, and the other's ETB rewards every re-entry. Free-running only when the blink is free or refunded (Deadeye + Drake class); otherwise a repeatable value engine.
• Mirrorhall Mimic // Ghastly Mimicry

  3U

  Creature — Spirit // Enchantment — AuraU

  One-shot copy enabler: a card enters as a copy of another (Phantasmal Image, Body Double, Phyrexian Metamorph), firing the partner's substantive ETB once. Not a repeating chain — fires once on entry — but valuable when the partner's ETB is combo-grade (graveyard reanimator, mana doubler, etc.).
• Saheeli Rai

  1UR

  Legendary Planeswalker — SaheeliRU

  Copy engine: one card makes a copy of a creature every turn, and the other's enter-the-battlefield effect rewards each copy. Real, repeatable value — the partner can't untap or re-enter the copier, so it never goes infinite.
• Godo, Bandit Warlord

  5R

  Legendary Creature — Human BarbarianR

  Both cards produce extra combat steps — their effects stack.
• Balthier and Fran

  1RG

  Legendary Creature — Human RabbitGR

  Both cards produce extra combat steps — their effects stack.
• Zariel, Archduke of Avernus

  2RR

  Legendary Planeswalker — ZarielR

  Both cards produce extra combat steps — their effects stack.
• Dino DNA

  1

  ArtifactC

  Copy engine: one card makes a copy of a creature every turn, and the other's enter-the-battlefield effect rewards each copy. Real, repeatable value — the partner can't untap or re-enter the copier, so it never goes infinite.
• Fury of the Horde

  5RR

  SorceryR

  Both cards produce extra combat steps — their effects stack.
• Waves of Aggression

  3R/WR/W

  SorceryRW

  Both cards produce extra combat steps — their effects stack.

• WithTempestra, Dame of Games1RR

  Copy chain: each card copies the other (or both copy a third), generating arbitrary copies. These two can't keep the loop going alone — add one of these to complete it:

  Breeches, Eager Pillager2RPoetic Ingenuity2RJ. Jonah Jameson2RRose Room Treasurer3RNuka-Cola Vending Machine3Gemcutter Buccaneer3R
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