Nightmare's Thirst 
Instant
You gain 1 life. Target creature gets -X/-X until end of turn, where X is the amount of life you gained this turn.
Legality
standardNOT LEGALpioneerLEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL
Instant
You gain 1 life. Target creature gets -X/-X until end of turn, where X is the amount of life you gained this turn.