Confidence:StrongSolidPlausibleTentativeSpeculative

• Mikaeus, the Unhallowed✓

  3BBB

  Legendary Creature — Zombie ClericB

  Death replacement: a death-replacement grant on one card lets the other repeatedly die-and-return for combo (Mikaeus + Walking Ballista class).
• Keiga, the Tide Star

  5U

  Legendary Creature — Dragon SpiritU

  Synergy between the two cards.
• Ruinous Waterbending

  1BB

  Sorcery — LessonB

  Both cards trigger when a creature dies — they fire together.
• Chandra, Torch of Defiance

  2RR

  Legendary Planeswalker — ChandraR

  Chandra, Torch of Defiance produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Scavenger Regent // Exude Toxin

  3BXBB

  Creature — Dragon // Sorcery — OmenB

  Scavenger Regent produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Chevill, Bane of Monsters

  BG

  Legendary Creature — Human RogueBG

  Both cards trigger when a creature dies — they fire together.
• Elesh Norn, Grand Cenobite

  5WW

  Legendary Creature — Phyrexian PraetorW

  Elesh Norn, Grand Cenobite produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Nicol Bolas, the Ravager // Nicol Bolas, the Arisen

  1UBR

  Legendary Creature — Elder Dragon // Legendary Planeswalker — BolasBRU

  Nicol Bolas, the Ravager produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Phlage, Titan of Fire's Fury

  1RW

  Legendary Creature — Elder GiantRW

  Phlage, Titan of Fire's Fury produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Sarkhan's Unsealing

  3R

  EnchantmentR

  Sarkhan's Unsealing produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Wrenn and Six

  RG

  Legendary Planeswalker — WrennGR

  Wrenn and Six produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Chandra, Flameshaper

  5RR

  Legendary Planeswalker — ChandraR

  Chandra, Flameshaper produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Banon, the Returners' Leader

  RW

  Legendary Creature — Human Cleric RebelRW

  Graveyard pair: one card brings creatures back from the graveyard repeatedly (or a creature that returns itself), and the other keeps feeding the loop — a recurring reanimator with a payoff, or a sacrifice outlet with a self-recurring creature.
• Chandra's Defeat

  R

  InstantR

  Chandra's Defeat produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Captivating Glance

  2U

  Enchantment — AuraU

  Captivating Glance temporarily takes control of an opponent's creature, and Yahenni, Undying Partisan sacrifices it — the opponent loses the permanent for good.
• Ugin, the Spirit Dragon

  8

  Legendary Planeswalker — UginC

  Ugin, the Spirit Dragon produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Lavabrink Floodgates

  3R

  ArtifactR

  Lavabrink Floodgates produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Form of the Dragon

  4RRR

  EnchantmentR

  Form of the Dragon produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Chandra, Hope's Beacon

  4RR

  Legendary Planeswalker — ChandraR

  Chandra, Hope's Beacon produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Hammerfist Giant

  4RR

  Creature — Giant WarriorR

  Hammerfist Giant produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Dragonback Assault

  3GUR

  EnchantmentGRU

  Dragonback Assault produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Hateful Eidolon

  B

  Enchantment Creature — SpiritB

  Both cards trigger when a creature dies — they fire together.
• Chandra, Pyromaster

  2RR

  Legendary Planeswalker — ChandraR

  Chandra, Pyromaster produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Nahiri, Storm of Stone

  2R/WR/W

  Legendary Planeswalker — NahiriRW

  Nahiri, Storm of Stone produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.
• Orcish Bowmasters

  1B

  Creature — Orc ArcherB

  Orcish Bowmasters produces damage that can kill creatures, enabling Yahenni, Undying Partisan's death-trigger or removal payoff.

• WithMikaeus, the Unhallowed3BBBB

  Death replacement: a death-replacement effect on one card lets the other survive lethal events. These two can't keep the loop going alone — add one of these to complete it:

  Nurgle's RotBBaloth Prime3GThe Sibsig CeremonyBBBXathrid Necromancer2BAvacyn's Collar1Golem Foundry3
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