Princess Yue

Whenever a spirit would die, you may sacrifice Princess Yue. If you do, choose one:
~Search your library for Yue, Spirit of the Moon
and put it into your hand.
~Until the end of your next turn, you may
subtract Princess Yue's converted mana cost
when playing Yue, Spirit of the Moon.

"The legends say the moon was the first waterbender.
Our ancestors saw how it pushed and pulled the tides,
and learned how to do it themselves."