Undying Scavenger

This creature enters the battlefild with a -1/-1
counter on it.
Whenever it becomes night, this creature gets
+1+1 until it becomes day.
This creature has undying as long as it has a
-1/-1 counter on it. If it does not, it has persist.
"Have you ever wondered about Phyrexian
werewolves? Surely they exi-" -Onurb, last words