Traveling Plague is a rare Enchantment — Aura card from Odyssey (ODY), collector number 166. Current market price: $0.36 (foil $1.59), TCGplayer market prices via Scryfall.
Enchant creature At the beginning of each upkeep, put a plague counter on this Aura. Enchanted creature gets -1/-1 for each plague counter on this Aura. When enchanted creature leaves the battlefield, that creature's controller returns this Aura from its owner's graveyard to the battlefield.