Feed the Earth

Cleave {b}{b}{g}{g} (You may cast this spell for its
cleave cost. If you do, remove the words in square
brackets.)
Exile all [non-token] creatures. At the beginning
of the next end step, return all creatures exiled
this way to the battlefield under their owner's
control. They become lands with "{t}: Add one
many of any color in this card's mana cost." and
lose all other types and abilities.