Kusari-Gama is a rare Artifact — Equipment card from Champions of Kamigawa (CHK), collector number 260. Current market price: $6.42 (foil $52.13), TCGplayer market prices via Scryfall.
Equipped creature has "{2}: This creature gets +1/+0 until end of turn." Whenever equipped creature deals damage to a blocking creature, this Equipment deals that much damage to each other creature defending player controls. Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)