Confidence:StrongSolidPlausibleTentativeSpeculative

• Reanimate

  B

  SorceryB

  Reanimate puts Keen Duelist onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Helping Hand

  W

  SorceryW

  Helping Hand puts Keen Duelist onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Unearth

  B

  SorceryB

  Unearth puts Keen Duelist onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Grave Researcher // Reanimate

  2BB

  Creature — Troll Warlock // SorceryB

  Grave Researcher puts Keen Duelist onto the battlefield from a graveyard without casting it, so its mana cost is never paid.
• Harmonic Prodigy

  1R

  Creature — Human WizardR

  Harmonic Prodigy makes Keen Duelist's triggered ability trigger an additional time — each time it fires, you get it twice. Value, not a loop.
• Delney, Streetwise Lookout

  2W

  Legendary Creature — Human ScoutW

  Delney, Streetwise Lookout makes Keen Duelist's triggered ability trigger an additional time — each time it fires, you get it twice. Value, not a loop.
• Roaming Throne

  4

  Artifact Creature — GolemC

  Roaming Throne makes Keen Duelist's triggered ability trigger an additional time — each time it fires, you get it twice. Value, not a loop.
• Mirror Room // Fractured Realm

  2U5UU

  Enchantment — Room // Enchantment — RoomU

  Mirror Room makes Keen Duelist's triggered ability trigger an additional time — each time it fires, you get it twice. Value, not a loop.
• Wizard's Staff

  1U

  Artifact — EquipmentU

  Wizard's Staff makes Keen Duelist's triggered ability trigger an additional time — each time it fires, you get it twice. Value, not a loop.