Emissary of Soulfire is a uncommon Creature — Djinn Monk card from Modern Horizons 3 (MH3), collector number 183. Current market price: $0.23 (foil $0.26), TCGplayer market prices via Scryfall.
When this creature enters, you get {E}{E}{E} (three energy counters). Pay {E}{E}: Put an exalted counter on target creature you control. Activate only as a sorcery. (Whenever a creature you control attacks alone, it gets +1/+1 until end of turn for each instance of exalted among permanents you control.)