Acornelia, Fashionable Filcher is a rare Legendary Creature — Squirrel card from Unsanctioned (UND), collector number 31. Current market price: $0.34, TCGplayer market prices via Scryfall.
Whenever you cast a spell with a squirrel in its art, you get {A} (an acorn counter). Whenever a Squirrel you control enters or dies, you get {A}. {2}{B}, Pay X {A}: Target creature gets -X/-X until end of turn. {G}, Pay X {A}: Target creature gets +X/+X until end of turn.