Non-artifact spells you cast have improvise. (Your artifacts can help cast non-artifact spells. Each artifact you tap after you're done activating mana abilities pays for 1.)
Illus. Kirsten Zirngibl
MYTHICSPOILER.COM THE CYCLICAL MTG SPOILER
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KHANS OF TARKIR 
COMMANDER 2014
FTV: ANNIHILATION 
SPEED vs CUNNING 
MAGIC 2015 
CONSPIRACY 
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