Sacrifice a creature. Gain an emblem that says "Draw a card at the start of your upkeep"
Which is pretty darn good. And it can still be used to exile someone's creature for a couple of turns if you're in a pinch or it's the only thing stopping you tromping home the win.
So wow. Is it meant to be in cost, instead of just perhaps? That would seem more reasonable (though still really quite good)
I'd say
if it was a card draw spell, 
if it was a removal spell. 
may be excessive.
You choose the X? This is then equivalent to:
Sacrifice a creature. Gain an emblem that says "Draw a card at the start of your upkeep"
Which is pretty darn good. And it can still be used to exile someone's creature for a couple of turns if you're in a pinch or it's the only thing stopping you tromping home the win.
So wow. Is it meant to be
in cost, instead of just 
perhaps? That would seem more reasonable (though still really quite good)