Dragonfire Blade is a rare Artifact — Equipment card from Tarkir: Dragonstorm (TDM), collector number 324. Current market price: $2.39 (foil $3.72), TCGplayer market prices via Scryfall.
Equipped creature gets +2/+2 and has hexproof from monocolored. Equip {4}. This ability costs {1} less to activate for each color of the creature it targets.