Firdoch Core is a common Kindred Artifact — Shapeshifter card from Lorwyn Eclipsed (ECL), collector number 255. Current market price: $0.31 (foil $1.09), TCGplayer market prices via Scryfall.
Changeling (This card is every creature type.) {T}: Add one mana of any color. {4}: This artifact becomes a 4/4 artifact creature until end of turn.