Morbid Curiosity
Sorcery
As an additional cost to cast this spell, sacrifice an artifact or creature.
Draw cards equal to the converted mana cost of the sacrificed permanent.
"Every creation carries a piece of its creators. Their knowledge, their dreams, their soul. That is the best part."
Illustrated by
Battlebond#149UncommonEnglishLegality
Rulings
Sep 20, 2016
If a permanent has 
in its mana cost, X is considered to be 0.
Sep 20, 2016
To determine how many cards to draw, use the converted mana cost of the permanent immediately before you sacrificed it.
Sep 20, 2016
If an effect copies Morbid Curiosity, the controller of the copy will draw the same number of cards as determined by the original. Its controller can’t and doesn’t have to sacrifice a permanent.