Sewer Plague 
Instant
Target creature an opponent controls perpetually gets -2/-2 and gains "At the beginning of each upkeep, this creature perpetually gets -1/-1."
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyNOT LEGALvintageNOT LEGALcommanderNOT LEGAL