Confidence:StrongSolidPlausibleTentativeSpeculative

• Silvanus's Invoker✓

  2G

  Creature — Dragon DruidG

  Untap loop: each side can untap what the other taps — a genuine mutual refresh engine.
• Wakeroot Elemental✓

  4GG

  Creature — ElementalG

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

  2R

  SorceryR

  Fiery Gambit untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• Innocuous Researcher

  3G

  Creature — Centaur DetectiveG

  Innocuous Researcher untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• 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.
• Candelabra of Tawnos

  1

  ArtifactC

  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.
• Beledros Witherbloom

  5BG

  Legendary Creature — Elder DragonBG

  Beledros Witherbloom untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• Formidable Speaker

  2G

  Creature — Elf DruidG

  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.
• Saryth, the Viper's Fang

  2GG

  Legendary Creature — Human WarlockG

  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.
• Prophet of Kruphix

  3GU

  Creature — Human WizardGU

  Prophet of Kruphix untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• Bumi, Unleashed

  3RG

  Legendary Creature — Human Noble AllyGR

  Bumi, Unleashed untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• Wilderness Reclamation

  3G

  EnchantmentG

  Wilderness Reclamation untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• Seedborn Muse

  3GG

  Creature — SpiritG

  Seedborn Muse untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• Sword of Feast and Famine

  3

  Artifact — EquipmentC

  Sword of Feast and Famine untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• Nature's Will

  2GG

  EnchantmentG

  Nature's Will untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• Emrakul, the Exigent Doom

  10

  Legendary Creature — EldraziC

  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.
• Awakening

  2GG

  EnchantmentG

  Awakening untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• Captain of the Mists

  2U

  Creature — Human WizardU

  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.
• Hope Tender

  1G

  Creature — Human DruidG

  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.
• Oboro Breezecaller

  1U

  Creature — Moonfolk WizardU

  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.
• Reset

  UU

  InstantU

  Reset untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• Elder Druid

  3G

  Creature — Elf Cleric DruidG

  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.
• Rude Awakening

  4G

  SorceryG

  Rude Awakening untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• Bear Umbra

  2GG

  Enchantment — AuraG

  Bear Umbra untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• Deserted Temple

  LandC

  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.