Mercurial Chemister

Oracle Text

U, T: Draw two cards.

R, T, Discard a card: Mercurial Chemister deals damage to target creature equal to the discarded card's converted mana cost.

Card Rulings

10/1/2012 If the discarded card has in its mana cost, X is 0.
10/1/2012 If the discarded card has no mana symbols in its upper right corner (because it’s a land card, for example), its converted mana cost is 0.