Myra, Flamecaller of Serr

Myra, Flamecaller of Serr's power is equal to the number of red instants and sorceries that you own
in your graveyard and exile.
Myra, Flamecaller of Serr's toughness is equal to
the number of black instants and sorceries that
you own in your graveyard and exile.
Whenever you cast an instant or sorcery create an
X/X Shadow token creature with shadow, where
X is the mana value of the spell.