Lunar-Etched Ritualist

Tap another untapped Druid or Shaman you control: The next creature spell you cast this turn has, "When this creature enters the battlefield, sacrifice all tapped creatures you control, then put X +1/+1 counters on this creature for each creature sacrificed this way."
Whenever you sacrifice one or more creatures, put a +1/+1 counter on Luna-Etched Ritualist.