Mephala, Lady of Whispers

Whenever a creature you control deals combat
damage to an opponent, you may sacrifice it.
If you do, target creature an opponent controls
can't attack or block until end of turn. At the
beginning of your upkeep, you may pay X life,
where X is the number of creatures an opponent
controls that can't attack or block. If you do,
create X 1/1 black Spider creature tokens with
reach.