Elf of Power

Teamwork of the Forest: For each green Elf creature
in your library, you may count it towards an
increase in the power and toughness of this
creature. So if your library has 4 elves, Elf of
Power gets +4/+4.
If Elf of Power has more than +10/+10
during any turn, exile Elf of Power from
the game.
{g}{g}{g}: Take control of target elf an opponent controls.