Kalamax, the Stormsire 
Legendary Creature — Elemental Dinosaur
Whenever you cast your first instant spell each turn, if Kalamax is tapped, copy that spell. You may choose new targets for the copy. Whenever you copy an instant spell, put a +1/+1 counter on Kalamax.
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyLEGALvintageLEGALcommanderLEGAL