Hideous Transmogrification

Destroy target creature and replace it with a black monstrosity token of equal power and toughness
under the control of a randomly selected player.
All non monstrosity creatures on the battlefield
gain a madness token, for each madness token on
a creature it gains +1/-1, if a creature would be
reduced to or below zero toughness in this way,
flip a coin and on heads it does damage to all
players equal to its power and is destroyed.
X is equal to the converted mana cost of target creature.