The Sporelock

You may mutate creatures in you graveyard onto
fungus creatures you control.
Whenever a creature you control mutates, surveil X
where X is the number of time that creature has
mutated.
{b/g}{b/g}{t}: target creature in your graveyard gains
mutate until end of turn, it's mutate cost is equal
to its mana cost.
"It may be dead, but it is not lost."