Confidence:StrongSolidPlausibleTentativeSpeculative

• Urtet, Remnant of Memnarch

  3

  Legendary Artifact Creature — MyrBGRUW

  Urtet, Remnant of Memnarch untaps all (or many) permanents, refreshing Birthing Boughs's tap activation.
• Osgood, Operation Double

  2UU

  Legendary Creature — Human Alien ShapeshifterU

  Both cards produce the same kind of effect (shared token subtype).
• Intellectual Offering

  4U

  InstantU

  Intellectual Offering untaps all (or many) permanents, refreshing Birthing Boughs's tap activation.
• Unstoppable Plan

  2U

  EnchantmentU

  Unstoppable Plan untaps all (or many) permanents, refreshing Birthing Boughs's tap activation.
• Seedborn Muse

  3GG

  Creature — SpiritG

  Seedborn Muse untaps all (or many) permanents, refreshing Birthing Boughs's tap activation.
• Unwinding Clock

  4

  ArtifactC

  Unwinding Clock untaps all (or many) permanents, refreshing Birthing Boughs's tap activation.
• Paradox Engine

  5

  Legendary ArtifactC

  Paradox Engine untaps all (or many) permanents, refreshing Birthing Boughs's tap activation.
• Dramatic Reversal

  1U

  InstantU

  Dramatic Reversal untaps all (or many) permanents, refreshing Birthing Boughs's tap activation.
• Blinkmoth Infusion

  12UU

  InstantU

  Blinkmoth Infusion untaps all (or many) permanents, refreshing Birthing Boughs's tap activation.
• Black Market Connections

  2B

  EnchantmentB

  Both cards produce the same kind of effect (shared token subtype).
• Springleaf Parade

  XGG

  EnchantmentG

  Both cards produce the same kind of effect (shared token subtype).
• The Bears of Littjara

  1GU

  Enchantment — SagaGU

  Both cards produce the same kind of effect (shared token subtype).
• Formless Genesis

  2G

  Kindred Sorcery — ShapeshifterG

  Both cards produce the same kind of effect (shared token subtype).
• Llanowar Druid

  1G

  Creature — Elf DruidG

  Refuel loop: one card's payoff untaps your lands, paying for the other's activation again — repeatable every turn, and often infinite.
• Personify

  1W

  InstantW

  Both cards produce the same kind of effect (shared token subtype).
• Stalactite Dagger

  2

  Artifact — EquipmentC

  Both cards produce the same kind of effect (shared token subtype).
• Belonging

  5W

  Creature — Elemental IncarnationW

  Both cards produce the same kind of effect (shared token subtype).
• Irregular Cohort

  2WW

  Creature — ShapeshifterW

  Both cards produce the same kind of effect (shared token subtype).
• Vizier of Many Faces

  2UU

  Creature — Shapeshifter ClericU

  Both cards produce the same kind of effect (shared token subtype).
• Maskwood Nexus

  4

  ArtifactC

  Both cards produce the same kind of effect (shared token subtype).
• Abundant Countryside

  LandC

  Both cards produce the same kind of effect (shared token subtype).
• Innocuous Researcher

  3G

  Creature — Centaur DetectiveG

  Innocuous Researcher untaps lands, fueling Birthing Boughs's mana-hungry effect.
• Fiery Gambit

  2R

  SorceryR

  Fiery Gambit untaps lands, fueling Birthing Boughs's mana-hungry effect.
• Time Spiral

  4UU

  SorceryU

  Time Spiral untaps lands, fueling Birthing Boughs's mana-hungry effect.
• Nissa, Vastwood Seer // Nissa, Sage Animist

  2G

  Legendary Creature — Elf Scout // Legendary Planeswalker — NissaG

  Nissa, Vastwood Seer untaps lands, fueling Birthing Boughs's mana-hungry effect.