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 The Darkness Crystal's tap activation.
• Unstoppable Plan

  2U

  EnchantmentU

  Unstoppable Plan untaps all (or many) permanents, refreshing The Darkness Crystal's tap activation.
• Seedborn Muse

  3GG

  Creature — SpiritG

  Seedborn Muse untaps all (or many) permanents, refreshing The Darkness Crystal's tap activation.
• Unwinding Clock

  4

  ArtifactC

  Unwinding Clock untaps all (or many) permanents, refreshing The Darkness Crystal'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 The Darkness Crystal's tap activation.
• Dramatic Reversal

  1U

  InstantU

  Dramatic Reversal untaps all (or many) permanents, refreshing The Darkness Crystal's tap activation.
• Blinkmoth Infusion

  12UU

  InstantU

  Blinkmoth Infusion untaps all (or many) permanents, refreshing The Darkness Crystal's tap activation.
• Bumi, Unleashed

  3RG

  Legendary Creature — Human Noble AllyGR

  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.
• Llanowar Druid

  1G

  Creature — Elf DruidG

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

  5UU

  Creature — IllusionU

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

  4U

  Creature — DrakeU

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

  5UU

  Creature — WhaleU

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

  3G

  Creature — Centaur DetectiveG

  Innocuous Researcher untaps lands, fueling The Darkness Crystal's mana-hungry effect.
• Fiery Gambit

  2R

  SorceryR

  Fiery Gambit untaps lands, fueling The Darkness Crystal's mana-hungry effect.
• Time Spiral

  4UU

  SorceryU

  Time Spiral untaps lands, fueling The Darkness Crystal's mana-hungry effect.
• Nissa, Vastwood Seer // Nissa, Sage Animist

  2G

  Legendary Creature — Elf Scout // Legendary Planeswalker — NissaG

  Nissa, Vastwood Seer untaps lands, fueling The Darkness Crystal's mana-hungry effect.
• Nissa, Worldwaker

  3GG

  Legendary Planeswalker — NissaG

  Nissa, Worldwaker untaps lands, fueling The Darkness Crystal's mana-hungry effect.
• Rewind

  2UU

  InstantU

  Rewind untaps lands, fueling The Darkness Crystal's mana-hungry effect.
• Prophet of Kruphix

  3GU

  Creature — Human WizardGU

  Prophet of Kruphix untaps lands, fueling The Darkness Crystal's mana-hungry effect.
• Finale of Revelation

  XUU

  SorceryU

  Finale of Revelation untaps lands, fueling The Darkness Crystal's mana-hungry effect.
• Zacama, Primal Calamity

  6RGW

  Legendary Creature — Elder DinosaurGRW

  Zacama, Primal Calamity untaps lands, fueling The Darkness Crystal's mana-hungry effect.
• Sphinx of the Second Sun

  6UU

  Creature — SphinxU

  Sphinx of the Second Sun untaps lands, fueling The Darkness Crystal's mana-hungry effect.