Caldera Dancers

When Caldera Dancers enters the battlefield, if
its stalk cost was paid, draw two cards, then
discard two cards.
Stalk {r}{r} (At the end of each block step, if there
is an unblocked creature attacking you, you may cast
this card for its stalk cost. If you do, choose an
unblocked creature attacking you. This creature blocks
that creature.)