Checks and Balances 

Enchantment
Cast this spell only if there are three or more players in the game. Whenever a player casts a spell, each of that player's opponents may discard a card. If they do, counter that spell.
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyNOT LEGALvintageNOT LEGALcommanderNOT LEGAL