Eternal Unicorn

Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)
Rejuvination ({ut}: Put a +1/+1 counter on this creature. Activate this ability only once each turn.)
"Legend tells that if you drink the unicorn's blood, you can live a hundred years longer." - Bob the Vampire