Everlasting Torment 

Enchantment
Players can't gain life. Damage can't be prevented. All damage is dealt as though its source had wither. (A source with wither deals damage to creatures in the form of -1/-1 counters.)
Legality
standardNOT LEGALpioneerNOT LEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL