Chaotic Strike 
Instant
Cast this spell only during combat after blockers are declared. Flip a coin. If you win the flip, target creature gets +1/+1 until end of turn. Draw a card.
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyLEGALvintageLEGALcommanderLEGAL