Scales of Life and Undeath

Creatures you control with +1/+1 counters
have persist. (When this creature dies, if it had
no -1/-1 counters on it, return it to the battlefield
under its owners control with a -1/-1 counter on it.)
Creatures you control with -1/-1 counters
have undying. (When this creature dies, if it had
no +1/+1 counters on it, return it to the battlefield
under its owners control with a +1/+1 counter on it.)