Erin, the Shadow Blade

{b}: Destroy target creature. You lose life equal to
it`s power.
{4}{g}{t}: All creatures you control get +X/+X,
where X is the number of Elves you control.
Erin, the Shadow Blade doesn`t untap during
your next untap step.
As long as you control Erin, the Shadow Blade, creatures you control can`t be destroyed
by spells or abilities.