Confidence:StrongSolidPlausibleTentativeSpeculative

• Najeela, the Blade-Blossom✓

  2R

  Legendary Creature — Human WarriorBGRUW

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

  2R

  EnchantmentR

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

  2BG

  Legendary Creature — Squirrel DruidBG

  Bear Umbra untaps all (or many) permanents, refreshing Hazel of the Rootbloom's tap activation.
• Ojer Taq, Deepest Foundation // Temple of Civilization

  4WW

  Legendary Creature — God // LandW

  Bear Umbra untaps all (or many) permanents, refreshing Ojer Taq, Deepest Foundation's tap activation.
• Mu Yanling, Sky Dancer

  1UU

  Legendary Planeswalker — YanlingU

  Bear Umbra untaps all (or many) permanents, refreshing Mu Yanling, Sky Dancer's tap activation.
• Lithoform Blight

  1B

  Enchantment — AuraB

  Bear Umbra untaps all (or many) permanents, refreshing Lithoform Blight's tap activation.
• Aclazotz, Deepest Betrayal // Temple of the Dead

  3BB

  Legendary Creature — Bat God // LandB

  Bear Umbra untaps all (or many) permanents, refreshing Aclazotz, Deepest Betrayal's tap activation.
• Alpine Moon

  R

  EnchantmentR

  Bear Umbra untaps all (or many) permanents, refreshing Alpine Moon's tap activation.
• Sea Gate Restoration // Sea Gate, Reborn

  4UUU

  Sorcery // LandU

  Bear Umbra untaps all (or many) permanents, refreshing Sea Gate Restoration's tap activation.
• Thousand Moons Smithy // Barracks of the Thousand

  2WW

  Legendary Artifact // Legendary Artifact LandW

  Bear Umbra untaps all (or many) permanents, refreshing Thousand Moons Smithy's tap activation.
• Isshin, Two Heavens as One

  RWB

  Legendary Creature — Human SamuraiBRW

  Isshin, Two Heavens as One makes Bear Umbra's triggered ability trigger an additional time — each time it fires, you get it twice. Value, not a loop.
• Wrenn and Realmbreaker

  1GG

  Legendary Planeswalker — WrennG

  Bear Umbra untaps all (or many) permanents, refreshing Wrenn and Realmbreaker's tap activation.
• Gaea's Cradle

  Legendary LandG

  Bear Umbra untaps all (or many) permanents, refreshing Gaea's Cradle's tap activation.
• Emeria's Call // Emeria, Shattered Skyclave

  4WWW

  Sorcery // LandW

  Bear Umbra untaps all (or many) permanents, refreshing Emeria's Call's tap activation.
• Windcrag Siege

  1RW

  EnchantmentRW

  Windcrag Siege makes Bear Umbra's triggered ability trigger an additional time — each time it fires, you get it twice. Value, not a loop.
• Great Divide Guide

  1G

  Creature — Human Scout AllyG

  Bear Umbra untaps all (or many) permanents, refreshing Great Divide Guide's tap activation.
• Welcome to . . . // Jurassic Park

  1GG

  Enchantment — Saga // Legendary LandG

  Bear Umbra untaps all (or many) permanents, refreshing Welcome to . . .'s tap activation.
• Sidequest: Catch a Fish // Cooking Campsite

  2W

  Enchantment // LandW

  Bear Umbra untaps all (or many) permanents, refreshing Sidequest: Catch a Fish's tap activation.
• Karakas

  Legendary LandW

  Bear Umbra untaps all (or many) permanents, refreshing Karakas's tap activation.
• Eumidian Hatchery

  LandB

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

  2G

  Legendary Creature — Treefolk MutantG

  Bear Umbra untaps all (or many) permanents, refreshing Harold and Bob, First Numens's tap activation.
• The Everflowing Well // The Myriad Pools

  2U

  Legendary Artifact // Legendary Artifact LandU

  Bear Umbra untaps all (or many) permanents, refreshing The Everflowing Well's tap activation.
• Abundant Growth

  G

  Enchantment — AuraG

  Bear Umbra untaps all (or many) permanents, refreshing Abundant Growth's tap activation.
• Joiner Adept

  1G

  Creature — Elf DruidG

  Bear Umbra untaps all (or many) permanents, refreshing Joiner Adept's tap activation.
• Ondu Inversion // Ondu Skyruins

  6WW

  Sorcery // LandW

  Bear Umbra untaps all (or many) permanents, refreshing Ondu Inversion's tap activation.