Champion of the Path is a rare Creature — Elemental Sorcerer card from Lorwyn Eclipsed (ECL), collector number 130. Current market price: $0.39 (foil $0.46), TCGplayer market prices via Scryfall.
As an additional cost to cast this spell, behold an Elemental and exile it. (Exile an Elemental you control or an Elemental card from your hand.) Whenever another Elemental you control enters, it deals damage equal to its power to each opponent. When this creature leaves the battlefield, return the exiled card to its owner's hand.