Expressive Firedancer is a common Creature — Human Sorcerer card from Secrets of Strixhaven (SOS), collector number 114. Current market price: $0.06 (foil $0.17), TCGplayer market prices via Scryfall.
Opus — Whenever you cast an instant or sorcery spell, this creature gets +1/+1 until end of turn. If five or more mana was spent to cast that spell, this creature also gains double strike until end of turn.