Trueheart Twins (AKH) from Amonkhet, available at 401 Games Canada.

• Rarity: Uncommon
• Finish: Normal
• Artist: Matt Stewart
• Card Text:
  You may exert Trueheart Twins as it attacks. (It won't untap during your next untap step.)
  Whenever you exert a creature, creatures you control get +1/+0 until end of turn.