Confidence:StrongSolidPlausibleTentativeSpeculative

• Derevi, Empyrial Tactician

  GWU

  Legendary Creature — Bird WizardGUW

  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.
• Intellectual Offering

  4U

  InstantU

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

  2U

  EnchantmentU

  Unstoppable Plan untaps all (or many) permanents, refreshing Bison Whistle's tap activation.
• Silken Strength

  1G

  Enchantment — AuraG

  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.
• Seedborn Muse

  3GG

  Creature — SpiritG

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

  4

  ArtifactC

  Unwinding Clock untaps all (or many) permanents, refreshing Bison Whistle's tap activation.
• Pestermite

  2U

  Creature — Faerie RogueU

  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.
• Giant-Sized Flying Ant

  3U

  Creature — InsectU

  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.
• Paradox Engine

  5

  Legendary ArtifactC

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

  1U

  InstantU

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

  12UU

  InstantU

  Blinkmoth Infusion untaps all (or many) permanents, refreshing Bison Whistle's tap activation.
• Rings of Brighthearth

  3

  ArtifactC

  Bison Whistle has activated abilities that aren't mana abilities, fueling Rings of Brighthearth's activation-trigger.
• Kurkesh, Onakke Ancient

  2RR

  Legendary Creature — Ogre SpiritR

  Bison Whistle has activated abilities that aren't mana abilities, fueling Kurkesh, Onakke Ancient's activation-trigger.