Watchful Naga 
Creature — Snake Wizard
You may exert this creature as it attacks. When you do, draw a card. (An exerted creature won't untap during your next untap step.)
Legality
standardNOT LEGALpioneerLEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL