Trueheart Twins is a uncommon Creature — Jackal Warrior card from Foundations Jumpstart (J25), collector number 605. Current market price: $0.27, TCGplayer market prices via Scryfall.
You may exert this creature 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.