Undying (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.)
It's what comes after that, so don't stray from the path.
Ulvenwald Monstrosity {GG} |Creature - Hound| 1/2 Undying (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.)