Youthful Rebellion

Whenever a creature enters the battlefield under
your control, you may have it fight target
creature you don't control. If you do, put a
+1/+1 counter on it.
"Those of us who have been around for centuries
respect the order the Seasonal Courts give us. These children who have only been around a handful of
decades don't truly understand what they are trying to destroy."
—Lullaby, Duke of Winter