Soul Impersonation

Destroy target creature. Create a token that is a
copy of it, except it's an Aura enchantment with
"Enchant target creature you control",
"Enchanted creature gets +X/+X, where X is this
cards converted mana cost," and "This card
becomes a creature if it's not attached to a
creature."
"Your form is distasteful to me, but if it will rid the
world of your kind, I will absorb every last one of you."
-Eristeg the Unbound