Mistmeadow Keeneye

When Mistmeadow Keeneye enters the battlefield, put a +1/+1 counter on up to one target creature and a -1/-1 counter on up to one target creature.
Whenever a creature with a counter on it dies,
put a +1/+1 counter on up to one target creature or put a -1/-1 counter on up to one target creature.
Shafts as painful as the adder's bite.