Tom Riddle, Cunning Child

{t}, Sacrifice target creature: Put target creature
with converted mana cost {x} or less from
graveyard to battlefield where {x} is converted
mana cost of sacrificed creature.
If a horcrux is on the battlefield, exile Tom
Riddle, Cunning Student. At the beginning of
next combat phase, return him to the battlefield
transformed.
"Did I know that I had just met the most
dangerous Dark wizard of all-time? No."
—Albus Dumbledore