Seeker of Sacrifice

When Seeker of Sacrifice enters the battlefield,
put a -2/-2 counter on another target creature
you control. If you can't, put a +1/+1 counter
on a target creature an opponent controls.
You may not apply your -2/-2 to a creature
you control that has a 0 for power or toughness.
In its search for power, it first seeks
out echoes of weakness.