Pi, AI Babysitter

Defender, Hero (You may tap any number of
Civilian creatures you control to pay for that much
mana towards casting this creature.)

When a non-artifact, non-Civilian creature enters
the battlefield under your control, put a +1/+1
counter on it. When a non-artifact Civilian creature
enters the battlefield under your control,
put two +1/+1 counters on it.