Avacyn's Collar is a uncommon Artifact — Equipment card from Dark Ascension (DKA), collector number 145. Current market price: $0.22 (foil $0.45), TCGplayer market prices via Scryfall.
Equipped creature gets +1/+0 and has vigilance. Whenever equipped creature dies, if it was a Human, create a 1/1 white Spirit creature token with flying. Equip {2}