Confidence:StrongSolidPlausibleTentativeSpeculative

• Rustvine Cultivator

  G

  Creature — Phyrexian Elf DruidG

  Untap loop: each side can untap what the other taps — a genuine mutual refresh engine.
• Trade Caravan

  W

  Creature — Human NomadW

  Untap loop: each side can untap what the other taps — a genuine mutual refresh engine.
• Lost Jitte

  1

  Legendary Artifact — EquipmentC

  Untap loop: each side can untap what the other taps — a genuine mutual refresh engine.
• Innocuous Researcher

  3G

  Creature — Centaur DetectiveG

  Innocuous Researcher untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• Jorn, God of Winter // Kaldring, the Rimestaff

  2G1UB

  Legendary Snow Creature — God // Legendary Snow ArtifactBGU

  Jorn, God of Winter untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• Prophet of Kruphix

  3GU

  Creature — Human WizardGU

  Prophet of Kruphix untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• Bumi, Unleashed

  3RG

  Legendary Creature — Human Noble AllyGR

  Bumi, Unleashed untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• Seedborn Muse

  3GG

  Creature — SpiritG

  Seedborn Muse untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• Wilderness Reclamation

  3G

  EnchantmentG

  Wilderness Reclamation untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• Sword of Feast and Famine

  3

  Artifact — EquipmentC

  Sword of Feast and Famine untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• Beledros Witherbloom

  5BG

  Legendary Creature — Elder DragonBG

  Beledros Witherbloom untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• Nature's Will

  2GG

  EnchantmentG

  Nature's Will untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• Patron of the Orochi

  6GG

  Legendary Creature — SpiritG

  Patron of the Orochi untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• Awakening

  2GG

  EnchantmentG

  Awakening untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• Woodland Guidance

  3G

  SorceryG

  Woodland Guidance untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• Haunted One

  2B

  Legendary Enchantment — BackgroundB

  Both cards trigger when a creature dies — they fire together.
• Bear Umbra

  2GG

  Enchantment — AuraG

  Bear Umbra untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• Sothera, the Supervoid

  2BB

  Legendary EnchantmentB

  Both cards trigger when a creature dies — they fire together.
• Hateful Eidolon

  B

  Enchantment Creature — SpiritB

  Both cards trigger when a creature dies — they fire together.
• The Meathook Massacre

  XBB

  Legendary EnchantmentB

  Both cards trigger when a creature dies — they fire together.
• Magus of the Candelabra

  G

  Creature — Human WizardG

  One-directional refresh: one card can untap permanents the other wants to reuse. Not self-sustaining on its own — the untapper has to keep showing up.
• The Serpent Society

  1BG

  Legendary Creature — Human Snake VillainBG

  Both cards trigger when a creature dies — they fire together.
• Endless Evil

  2U

  Enchantment — AuraU

  Both cards trigger when a creature dies — they fire together.
• Wight

  1B

  Creature — Zombie SoldierB

  Both cards trigger when a creature dies — they fire together.
• Meren of Clan Nel Toth

  2BG

  Legendary Creature — Human ShamanBG

  Both cards trigger when a creature dies — they fire together.