Confidence:StrongSolidPlausibleTentativeSpeculative

• Legolas's Quick Reflexes

  G

  InstantG

  Legolas's Quick Reflexes can kill creatures (with damage or by shrinking them), enabling Cauldron of Souls's death-trigger or removal payoff.
• Intellectual Offering

  4U

  InstantU

  Intellectual Offering untaps all (or many) permanents, refreshing Cauldron of Souls's tap activation.
• Unstoppable Plan

  2U

  EnchantmentU

  Unstoppable Plan untaps all (or many) permanents, refreshing Cauldron of Souls's tap activation.
• Iron Fist, Living Weapon

  2R

  Legendary Creature — Human Warrior HeroR

  Iron Fist, Living Weapon can kill creatures (with damage or by shrinking them), enabling Cauldron of Souls's death-trigger or removal payoff.
• Unwinding Clock

  4

  ArtifactC

  Unwinding Clock untaps all (or many) permanents, refreshing Cauldron of Souls's tap activation.
• Seedborn Muse

  3GG

  Creature — SpiritG

  Seedborn Muse untaps all (or many) permanents, refreshing Cauldron of Souls's tap activation.
• Setessan Tactics

  1G

  InstantG

  Setessan Tactics can kill creatures (with damage or by shrinking them), enabling Cauldron of Souls's death-trigger or removal payoff.
• Paradox Engine

  5

  Legendary ArtifactC

  Paradox Engine untaps all (or many) permanents, refreshing Cauldron of Souls's tap activation.
• Captain Rex Nebula

  1RW

  Legendary Creature — Human Pilot EmployeeRW

  Captain Rex Nebula can kill creatures (with damage or by shrinking them), enabling Cauldron of Souls's death-trigger or removal payoff.
• Dramatic Reversal

  1U

  InstantU

  Dramatic Reversal untaps all (or many) permanents, refreshing Cauldron of Souls's tap activation.
• Voldaren Thrillseeker

  2R

  Creature — Vampire WarriorR

  Voldaren Thrillseeker can kill creatures (with damage or by shrinking them), enabling Cauldron of Souls's death-trigger or removal payoff.
• Brawl

  3RR

  InstantR

  Brawl can kill creatures (with damage or by shrinking them), enabling Cauldron of Souls's death-trigger or removal payoff.
• Blinkmoth Infusion

  12UU

  InstantU

  Blinkmoth Infusion untaps all (or many) permanents, refreshing Cauldron of Souls's tap activation.
• Thunder of Unity

  RWB

  Enchantment — SagaBRW

  Cauldron of Souls gives a creature persist that returns it once when it dies, re-firing Thunder of Unity's death or enter-the-battlefield trigger.
• Kurkesh, Onakke Ancient

  2RR

  Legendary Creature — Ogre SpiritR

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

  3

  ArtifactC

  Cauldron of Souls has activated abilities that aren't mana abilities, fueling Rings of Brighthearth's activation-trigger.