Gravekeeper's Supernaturalist

When Gravekeeper's Supernaturalist enters the battlefield, you may sacrifice a creature. This card
gains +X/+X, where X is that creature's
converted mana cost.
While you control "Necrovalley", this card and "Necrovalley" gain indestructible.
At the beginning of your end step, you may
search your library for a white and black
Cleric or a card that lists "Necrovalley" in its
text, put that card in your hand, then shuffle
your library.