Samira, the Desert Rose

Whenever Samira deals damage, she gets a grade counter in this order; E, D, C, B, A, S.
Samira gets +1/+1 for each grade above E she
has.
{t} Samira deals 6 damage to each other creature and planeswalker, 12 damage to each opponent, and add {r}{r}{r} to your mana pool. Only use when Samira has S grade.