Confidence:StrongSolidPlausibleTentativeSpeculative

• Reanimate

  B

  SorceryB

  Reanimate puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Fiery Gambit

  2R

  SorceryR

  Fiery Gambit untaps lands, fueling Fireborn Knight's mana-hungry effect.
• Grave Researcher // Reanimate

  2BB

  Creature — Troll Warlock // SorceryB

  Grave Researcher puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Innocuous Researcher

  3G

  Creature — Centaur DetectiveG

  Innocuous Researcher untaps lands, fueling Fireborn Knight's mana-hungry effect.
• Time Spiral

  4UU

  SorceryU

  Time Spiral untaps lands, fueling Fireborn Knight's mana-hungry effect.
• Sefris of the Hidden Ways

  WUB

  Legendary Creature — Human WizardBUW

  Sefris of the Hidden Ways puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Recurring Nightmare

  2B

  EnchantmentB

  Recurring Nightmare puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Priest of Fell Rites

  WB

  Creature — Human WarlockBW

  Priest of Fell Rites puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Nissa, Vastwood Seer // Nissa, Sage Animist

  2G

  Legendary Creature — Elf Scout // Legendary Planeswalker — NissaG

  Nissa, Vastwood Seer untaps lands, fueling Fireborn Knight's mana-hungry effect.
• Animate Dead

  1B

  Enchantment — AuraB

  Animate Dead puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Exhume

  1B

  SorceryB

  Exhume puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Life // Death

  G1B

  Sorcery // SorceryBG

  Life puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Elrond, Moon-Reader

  2U

  Legendary Creature — Elf NobleU

  Fireborn Knight has activated abilities that aren't mana abilities, fueling Elrond, Moon-Reader's activation-trigger.
• Dance of the Dead

  1B

  Enchantment — AuraB

  Dance of the Dead puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Victimize

  2B

  SorceryB

  Victimize puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Persist

  1B

  SorceryB

  Persist puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Soul Exchange

  BB

  SorceryB

  Soul Exchange puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Rewind

  2UU

  InstantU

  Rewind untaps lands, fueling Fireborn Knight's mana-hungry effect.
• Beledros Witherbloom

  5BG

  Legendary Creature — Elder DragonBG

  Beledros Witherbloom untaps lands, fueling Fireborn Knight's mana-hungry effect.
• Finale of Revelation

  XUU

  SorceryU

  Finale of Revelation untaps lands, fueling Fireborn Knight's mana-hungry effect.
• Ascent of the Worthy

  1WB

  Enchantment — SagaBW

  Ascent of the Worthy puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Prophet of Kruphix

  3GU

  Creature — Human WizardGU

  Prophet of Kruphix untaps lands, fueling Fireborn Knight's mana-hungry effect.
• Necromancy

  2B

  EnchantmentB

  Necromancy puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Too Evil to Stay Dead

  2B

  SorceryB

  Too Evil to Stay Dead puts Fireborn Knight onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Bumi, Unleashed

  3RG

  Legendary Creature — Human Noble AllyGR

  Bumi, Unleashed untaps lands, fueling Fireborn Knight's mana-hungry effect.