Contaminated Bond 
Enchantment — Aura
Enchant creature (Target a creature as you cast this. This card enters attached to that creature.) Whenever enchanted creature attacks or blocks, its controller loses 3 life.
Legality
standardNOT LEGALpioneerNOT LEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL