Stag Patronus

Whenever enchanted creature attacks, put a
+1/+1 counter on enchanted creature. Then if it
has three or more +1/+1 counters on it, sacrifice
Stag Patronus.
When enchanted creature becomes the target of a
spell or ability your opponent controls, sacrifice
Stag Patronus.
Whenever Stage Patronus is sacrificed, enchanted creature gains indestructible until end of turn.