Oath of Mages 

Enchantment
At the beginning of each player's upkeep, that player chooses target player who has more life than they do and is their opponent. The first player may have this enchantment deal 1 damage to the second player.
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyLEGALvintageLEGALcommanderLEGAL