Insidious Corruption

When Insidious Corruption enters the battle-
field, choose a target creature.
{t}: Target creature gets -1/-1.
{x},{t}: Target creature gets -1/-1 and -X/-X,
where X equals to {b}.
"Being possessed by spirits can be terrible. But being possessed by a corrupt spirit is indescribable! It's like
a cloud of acidic gas invading your body."