Lyx Messan Silencer

Whenever Lyx Messan Silencer blocks a creature, the power of the creature it's blocking becomes 0.
Stalk {1}{u}{u} (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.)