Concussion

Enchant target creature
This creature gains -1/-1. Whenever this creature
takes damage, it takes it in -1/-1 counters. If the creature was to be removed from the battlefield,
gain control of it and pick a new target for
Concussion.
"If you resume play with a concussion, you have a
chance of making a concussion worse, and we don't
want that, now do we." -Players who want your creatures gone