Confidence:StrongSolidPlausibleTentativeSpeculative

• Tolarian Kraken

  4UU

  Creature — KrakenU

  Untap loop: each side can untap what the other taps — a genuine mutual refresh engine.
• Baron Helmut Zemo

  BBB

  Legendary Creature — Human Noble VillainB

  Copy engine: one card makes a copy of a creature every turn, and the other's enter-the-battlefield effect rewards each copy. Real, repeatable value — the partner can't untap or re-enter the copier, so it never goes infinite.
• Copperhorn Scout

  G

  Creature — Elf ScoutG

  Copperhorn Scout untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• White Plume Adventurer

  2W

  Creature — Orc ClericW

  White Plume Adventurer untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Jace, Ingenious Mind-Mage

  4UU

  Legendary Planeswalker — JaceU

  Jace, Ingenious Mind-Mage untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Aggravated Assault

  2R

  EnchantmentR

  Aggravated Assault untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• The Thirteenth Doctor

  1GU

  Legendary Creature — Time Lord DoctorGU

  The Thirteenth Doctor untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Veteran Beastrider

  1GW

  Creature — Human KnightGW

  Veteran Beastrider untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Merrow Commerce

  1U

  Kindred Enchantment — MerfolkU

  Merrow Commerce untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Drumbellower

  2W

  Creature — SpiritW

  Drumbellower untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Gideon, Martial Paragon

  4W

  Legendary Planeswalker — GideonW

  Gideon, Martial Paragon untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Deepway Navigator

  WU

  Creature — Merfolk WizardUW

  Deepway Navigator untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Dazzling Theater // Prop Room

  3W2W

  Enchantment — Room // Enchantment — RoomW

  Dazzling Theater untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Intellectual Offering

  4U

  InstantU

  Intellectual Offering untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Dino DNA

  1

  ArtifactC

  Copy engine: one card makes a copy of a creature every turn, and the other's enter-the-battlefield effect rewards each copy. Real, repeatable value — the partner can't untap or re-enter the copier, so it never goes infinite.
• Prophet of Kruphix

  3GU

  Creature — Human WizardGU

  Prophet of Kruphix untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Éomer, Marshal of Rohan

  2RR

  Legendary Creature — Human KnightR

  Éomer, Marshal of Rohan untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Ivorytusk Fortress

  2WBG

  Creature — ElephantBGW

  Ivorytusk Fortress untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Unstoppable Plan

  2U

  EnchantmentU

  Unstoppable Plan untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Plargg, Dean of Chaos // Augusta, Dean of Order

  1R2W

  Legendary Creature — Orc Shaman // Legendary Creature — Human ClericRW

  Plargg, Dean of Chaos untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Najeela, the Blade-Blossom

  2R

  Legendary Creature — Human WarriorBGRUW

  Najeela, the Blade-Blossom untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Rionya, Fire Dancer

  3RR

  Legendary Creature — Human WizardR

  Copy engine: one card makes a copy of a creature every turn, and the other's enter-the-battlefield effect rewards each copy. Real, repeatable value — the partner can't untap or re-enter the copier, so it never goes infinite.
• Betor, Kin to All

  2WBG

  Legendary Creature — Spirit DragonBGW

  Betor, Kin to All untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Combat Celebrant

  2R

  Creature — Human WarriorR

  Combat Celebrant untaps all (or many) permanents, refreshing Tempest Harvester's tap activation.
• Helm of the Host

  4

  Legendary Artifact — EquipmentC

  Copy engine: one card makes a copy of a creature every turn, and the other's enter-the-battlefield effect rewards each copy. Real, repeatable value — the partner can't untap or re-enter the copier, so it never goes infinite.