Saya, the Unmaker of Worlds

After an opponent casts a creature spell, put a
spore counter on it.
{3}{u}{b}: If you control a human, Sacrifice Saya,
the Unmaker of Worlds, the creatures with a
spore counter on it lose all abilities and become a
black Eldritch Horror creature with its original
base power and toughness.(It loses all other
card types and creature types.) Gain control
of all creatures with a spore counter on it.