Rite of the Witch-Maw

Whenever an opponent casts a spell, put a charge counter on Rite of the Witch-Maw.
At the beginning of your pre combat main phase,
add {c} to your mana pool for each charge counter
on Rite of the Witch-Mae, then, if Rite of the
Witch-Maw has five or more charge counters on
it, nontoken creatures you control have prowess
until end of turn.