Gravetide Pixie

If {b} was spent to cast Gravetide Pixie, it's power
and toughness are each equal to the number of creatures in target opponents graveyard, and it
gains deathtouch.
If {g} was spent to cast Gravetide Pixie, it's power
and toughness are each equal to the number of creatures target opponent controls, and it gains
trample.