Emberstrike Duo is a common Creature — Elemental Warrior Shaman card from Shadowmoor (SHM), collector number 185. Current market price: $0.15 (foil $0.09), TCGplayer market prices via Scryfall.
Whenever you cast a black spell, this creature gets +1/+1 until end of turn. Whenever you cast a red spell, this creature gains first strike until end of turn.