Confidence:StrongSolidPlausibleTentativeSpeculative

• Intruder Alarm✓

  2U

  EnchantmentU

  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.
• Sky Hussar

  3WU

  Creature — Human KnightUW

  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.
• Aura of Dominion

  UU

  Enchantment — AuraU

  Token-fuel engine: one side keeps producing untapped tokens that pay the other's tap costs, and the output feeds the loop again — Squirrel Nest with Earthcraft is the classic shape.
• Waylay

  2W

  InstantW

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

  G

  Creature — Elf ScoutG

  Copperhorn Scout untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• White Plume Adventurer

  2W

  Creature — Orc ClericW

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

  4UU

  Legendary Planeswalker — JaceU

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

  2R

  EnchantmentR

  Aggravated Assault untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• The Thirteenth Doctor

  1GU

  Legendary Creature — Time Lord DoctorGU

  The Thirteenth Doctor untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• Veteran Beastrider

  1GW

  Creature — Human KnightGW

  Veteran Beastrider untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• Drumbellower

  2W

  Creature — SpiritW

  Drumbellower untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• Gideon, Martial Paragon

  4W

  Legendary Planeswalker — GideonW

  Gideon, Martial Paragon untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• Dazzling Theater // Prop Room

  3W2W

  Enchantment — Room // Enchantment — RoomW

  Dazzling Theater untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• Intellectual Offering

  4U

  InstantU

  Intellectual Offering untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• Dion, Bahamut's Dominant // Bahamut, Warden of Light

  3W

  Legendary Creature — Human Noble Knight // Legendary Enchantment Creature — Saga DragonW

  Both cards produce the same kind of effect (shared token subtype).
• Aryel, Knight of Windgrace

  2WB

  Legendary Creature — Human KnightBW

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

  3GU

  Creature — Human WizardGU

  Prophet of Kruphix untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• Éomer, Marshal of Rohan

  2RR

  Legendary Creature — Human KnightR

  Éomer, Marshal of Rohan untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• Ivorytusk Fortress

  2WBG

  Creature — ElephantBGW

  Ivorytusk Fortress untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• Unstoppable Plan

  2U

  EnchantmentU

  Unstoppable Plan untaps all (or many) permanents, refreshing Xerex Strobe-Knight'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 Xerex Strobe-Knight's tap activation.
• Najeela, the Blade-Blossom

  2R

  Legendary Creature — Human WarriorBGRUW

  Najeela, the Blade-Blossom untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• Betor, Kin to All

  2WBG

  Legendary Creature — Spirit DragonBGW

  Betor, Kin to All untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• Combat Celebrant

  2R

  Creature — Human WarriorR

  Combat Celebrant untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.
• Aurelia, the Warleader

  2RRWW

  Legendary Creature — AngelRW

  Aurelia, the Warleader untaps all (or many) permanents, refreshing Xerex Strobe-Knight's tap activation.