Martani, Princess of the Elves

{t} {g}{g} elves you control get +1+1
until end of turn.
If you control 5 or more elves, put a +1 +1
counter on them instead
{ut} {b}{b}{g}{g} sacrifice an elf: if it was a black elf
put a -1 -1
counter on a creature your opponent controls,
if it was a green elf, gain 3 life