Morgbiff, the Silent Stepper

When Morgbiff, the Silent Stepper enters the battlefield, destroy all creatures with converted mana cost x, where x is the x in casting Morgbiff, the Silent Stepper. {t} return target creature from a graveyard to the battlefield under your control. {r}{u}{u/b}{x}{t} x amount of creatures get +X/+X where X is the mana you spent in the X while casting Morgbiff, the Slient Stepper.