Morbid Curiosity
Kaladesh — uncommon
Sorcery
Morbid Curiosity rulings:
2016-09-20: If a permanent has in its mana cost, X is considered to be 0.
2016-09-20: To determine how many cards to draw, use the mana value of the permanent immediately before you sacrificed it.
2016-09-20: 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.